Objective:Tyrosinase is the rate-limiting enzyme in the generation of melanin.The feline tyrosinase mutation,G302R,confers temperature-sensitive loss of function,resulting in the familiar Siamese cat phenotype.Crystal...Objective:Tyrosinase is the rate-limiting enzyme in the generation of melanin.The feline tyrosinase mutation,G302R,confers temperature-sensitive loss of function,resulting in the familiar Siamese cat phenotype.Crystal or cryoEM structures are elusive for any mammalian tyrosinase to date.Protein misfolding is suggested as a basis for phenotypes resulting frommutant tyrosinases,but this hypothesis needs structural confirmation.Our objective for this study is to confirm misfolding of mutant tyrosinase as a basis for temperature-sensitive phenotypes compared to catalytic dysfunction that may be responsible for other tyrosinase mutant breed phenotypes.Methods:We have employed AlphaFold3 to compare structural alignments of four well-characterized feline tyrosinase mutations to wild type(WT)feline tyrosinase;SiameseG302R,Burmese G227W,Mocha delI274-L312+2aa,andAlbino del401-529 lacking the transmembrane and C-terminus domains.Results:The manifestations of the bulkier side chains of the Siamese positively charged arginine(R)and the Burmese hydrophobic tryptophan(W)are evident locally.But interestingly,the major differences between the structures lie in the usually ignored signal peptide(SP)regions of each mutant.As the maturation of the nascent tyrosinase peptide is highly dependent on accurate and early cleavage of the SP,we hypothesize these structural anomaliesmay formthe basis formisfolded or truncated final enzyme forms,leading to the observed phenotypes seen in these cats.Conclusions:We have identified enzyme dysfunction and protein misfolding as separate mechanisms for feline coat phenotypes resulting from tyrosinase mutations.展开更多
Pimenta dioica is a tropical Caribbean tree belonging to the family Myrtaceae,widely used in various human activities,including perfume production,food flavoring,natural pesticides,and medicine.This study aimed to exp...Pimenta dioica is a tropical Caribbean tree belonging to the family Myrtaceae,widely used in various human activities,including perfume production,food flavoring,natural pesticides,and medicine.This study aimed to explore the chemical composition of Pimenta dioica flower essential oil obtained via hydrodistillation using GC-MS analysis.Additionally,the oil’s tyrosinase inhibitory activity was investigated.The effectiveness of the oil’s major constituents in binding to tyrosinase was also evaluated through molecular docking simulations.GC-MS analysis identified fifteen compounds,with eugenol(70.59%)as the major component,followed byβ-myrcene(10.54%),limonene(8.55%),β-ocimene(4.92%),α-phellandrene(1.39%),and linalool(1.46%).The oil exhibited tyrosinase inhibitory activity with an IC_(50) value of 28.65±0.77μg/mL,compared to kojic acid(IC_(50)=1.94±0.53μg/mL).It also showed moderate antioxidant activity with an IC_(50) of 5.41±0.68μg/mL,relative to quercitrin(0.78±0.37μg/mL).Molecular docking studies revealed that the six identified constituents exhibited good binding affinity and fitting to the tyrosinase active site,as indicated by docking scores and specific interactions.These interactions likely contribute to the overall inhibitory effect through multiple binding modes.The findings suggest that the monoterpene content plays a crucial role in the observed inhibitory activity and enhance our understanding of natural compounds as potential therapeutics for tyrosinase-related disorders.Therefore,P.dioica flower essential oil may represent a safe and effective natural source of skin-whitening agents for cosmetic and pharmaceutical applications.Further investigations,including in vivo studies,pharmacokinetics,pharmacodynamics,and toxicity profiling,are recommended.展开更多
[Objective] The paper was to study the activity of tyrosinase,so as to provide reference for preventing browning of potatoes as well as fruits and vegetables containing tyrosinase.[Method] With potato as raw material ...[Objective] The paper was to study the activity of tyrosinase,so as to provide reference for preventing browning of potatoes as well as fruits and vegetables containing tyrosinase.[Method] With potato as raw material and Na2HPO4-HCl in buffer solution（pH=7.2）as system,spectrophotometer was used to measure the absorbance of potato extract at 480nm,the curve was established,and the activity of tyrosinase was obtained.[Result] The changes of data were little under the above conditions,and the stability of tyrosinase activity was high.[Conclusion] Using spectrophotometry to determine the tyrosinase activity in potato is simple with high accuracy.展开更多
[Objective] This study aimed to analyze tyrosinase activity and its expression in Varicorhinus macrolepis. [Method] V. macrolepis was used as experimental material for the analysis and research of tyrosinase in nine k...[Objective] This study aimed to analyze tyrosinase activity and its expression in Varicorhinus macrolepis. [Method] V. macrolepis was used as experimental material for the analysis and research of tyrosinase in nine kinds of organs and tissues of male and female V. macrolepis individuals by using polyacrylamide gel electrophoresis and biochemical staining method, spectrophotometry and enzyme histochemical technology. [Result] Tyrosinase exists in the liver and pancreas, intestine and spleen of female and male V. macrolepis and in the gallbladder of male V. macrolepis. Tyrosinase activities in various tissues of V. macrolepis varied largely. Specifically, tyrosinase activities in the spleen was the maximum, which was higher in female V. macrolepis than in males. According to the enzyme histochemistry results, strong positive signals of tyrosinase existed in the spleen, intestine, liver and pancreas and gallbladder of V. macrolepis, which was the strongest in the spleen. [Conclusion] In this paper, research on tissue localization of tyrosinase in V. macrolepis had been first reported, which provided theoretical basis for further exploring the functions of tyrosinase in V. macrolepis.展开更多
Objective] Tyrosinase is a kind of polyphenol oxidase used widely, and the study of tyrosinase attracts extensive attention. [Method] ln this experiment, A conversion kinetic curve of dopa solution was obtained using ...Objective] Tyrosinase is a kind of polyphenol oxidase used widely, and the study of tyrosinase attracts extensive attention. [Method] ln this experiment, A conversion kinetic curve of dopa solution was obtained using absorbance of potato extract at 480 nm in Na2HPO4-HCl buffer system at a pH value of 7.2 with the vari-ation rate of absorbance against time （ΔA/Δt） as reaction rate, and the activity of tyrosinase could thus be calculated. [Result] The results showed that at the wave-length, in the Na2HPO4-HCl buffer system with a pH value at 7.2, there was little in-terference to the system, the data showed smal fluctuations, and the activity of ty-rosinase was high and stable, further providing a theoretical foundation for the de-termination and study of factors influencing tyrosinase activity. [Conclusion] The catalytic activity of tyrosinase was studied and determined with buffer solution as substrate with high accuracy and good effect.展开更多
Four series of derivatives of vanillin,anisaldehyde,genistein and aloe emodin were prepared.The single crystal of （E）-1-（5-（4-methoxyphenyl）-3-（4-methoxystyryl）-4,5-dihydro-1H-pyrazol-1-yl）ethanone,which was s...Four series of derivatives of vanillin,anisaldehyde,genistein and aloe emodin were prepared.The single crystal of （E）-1-（5-（4-methoxyphenyl）-3-（4-methoxystyryl）-4,5-dihydro-1H-pyrazol-1-yl）ethanone,which was synthesized from vanillin, was obtained by spontaneous evaporation method.All the compounds were tested for the tyrosinase inhibitory activities.The results demonstrated that the IC_（50）values of vanillin,anisaldehyde,genistein and aloe emodin against mushroom tyrosinase activity are 68,49,343 and 160μM,respectively.Among the twelve derivatives,（E）-1-（5-（4-methoxyphenyl）-3-（4-methoxystyryl）-4,5- dihydro-1H-pyrazol-1-yl）ethanone from vanillin and 4,5-dimethoxy-9,10-dioxo-9,10-dihydroanthracene-2-carboxylic acid from aloe emodin showed good inhibition against the tyrosinase with IC_（50）values of 18μM and 21μM,respectively.展开更多
The inhibitory effect of ferulic acid on the diphenolase activity of mushroom tyrosinase and the kinetic behavior were studied with L-3,4-dihydroxyphenylalanine （L-DOPA） as substrate. The inhibitor concentration lea...The inhibitory effect of ferulic acid on the diphenolase activity of mushroom tyrosinase and the kinetic behavior were studied with L-3,4-dihydroxyphenylalanine （L-DOPA） as substrate. The inhibitor concentration leading to 50% relative activity lost （IC50） was estimated to be 0.15 mmol·L^-1. The inhibition mechanism obtained from Lineweaver-Burk plots shows that ferulic acid is a competitive inhibitor and the inhibition of tyrosinase by ferulic acid is a reversible reaction. The equilibrium constant for ferulic acid binding with the tyrosinase was determined to be 0.25 mmol·L^-1 for diphenolase. Keywords tyrosinase, ferulic acid, kinetics, inhibition, L-DOPA, diphenolase展开更多
Objective:To investigate the suitability of citrus-press cakes,by-products of the juice industry as a source for the whitening agents for cosmetic industry.Methods:Ethylacetate extracts of citrus-press cakes(CCE)were ...Objective:To investigate the suitability of citrus-press cakes,by-products of the juice industry as a source for the whitening agents for cosmetic industry.Methods:Ethylacetate extracts of citrus-press cakes(CCE)were examined for their anti-melanogenic potentials in terms of the inhibition of melanin production and mechanisim of melanogenesis by using Western Blot analysis with tyrosinese,tyrosinase-related protein-1(TRP-1),TRP2,and microphthalmia-associated transcription factor(MITF)proteins.To apply the topical agents,citrus-press cakes was investigated the safety in human skin cell line.Finally flavonoid analysis of CCE was also determined by HPLC analysis.Results:Results indicated that CCE were shown to down-regulate melanin content in a dose-dependent pattern.The CCE inhibited tyrosinase,TRP-2,and MITF expressions in a dose-dependent manner.To test the applicability of CCE to human skin,we used MTT assay to assess the cytotoxic effects of CCE on human keratinocyte HaCaT cells.The CCE exhibited low cytotoxicity at 50μg/mL.Characterization of the citrus-press cakes for flavonoid contents using HPLC showed varied quantity of rutin,narirutin,and hesperidin.Conclusions:Considering the anti-melanogenic activity and human safety,CCE is considered as a potential anti-melanogenic agent and may be effective for topical application for treating hyperpigmentation disorders.展开更多
Aqueous ethanol extracts of powdered stems of Dendrobium loddigesii afforded three new phenolics including threo-7-Oethyl-9-O-(4-hydroxyphenyl)propionyl-guaiacylglycerol(1),(R)-4,5,4ʹ-trihydroxy-3,3ʹ,α-trimethoxybibe...Aqueous ethanol extracts of powdered stems of Dendrobium loddigesii afforded three new phenolics including threo-7-Oethyl-9-O-(4-hydroxyphenyl)propionyl-guaiacylglycerol(1),(R)-4,5,4ʹ-trihydroxy-3,3ʹ,α-trimethoxybibenzyl(2)and(S)-5,5′,7-trihydroxy-3′,4′-dimethoxyflavanone(3),together with eleven known analogues.Their structures were determined by extensive spectroscopic analysis.To identify natural antioxidants,whitening,and anti-aging agents,the abilities of these phenolics were assessed to scavenge the 1,2-diphenyl-2-picrylhydrazyl(DPPH)radical,their abilities to inhibit tyrosinase production,and their abilities to stimulate collagen production by human dermal fibroblasts-adult(HDFa)assay.It was found that compounds 1,4-8,13 and 14 exhibited significant DPPH radical scavenging activities,compound 10 exhibited tyrosinase inhibitory activity(IC_(50)37.904μg/mL),and compound 9 showed significant collagen production with an EC_(50)value of 3.182μg/mL.These results suggest that phenolic constituents from D.loddigesii may be candidate antioxidants,skin-whitening and/or anti-aging agents.展开更多
Tyrosinase is an important enzyme in controlling the formation of melanin in melanosome,and plays a key role in the pigmentation of hair and skin.The abnormal expression or activation of tyrosinase is associated with ...Tyrosinase is an important enzyme in controlling the formation of melanin in melanosome,and plays a key role in the pigmentation of hair and skin.The abnormal expression or activation of tyrosinase is associated with several diseases such as albinism,vitiligo,melanoma and Parkinson disease.Excessive deposition of melanin could cause diseases such as freckles and brown spots in the human body,and it is also closely related to browning of fruits and vegetables and insect molting.Detecting and inhibiting the activity of tyrosinase is of extraordinary value in the progress of diagnosis and treatment of these diseases.Therefore,many selective optical detection probes and small molecular inhibitors have been developed,and have made significant contributions to the basic and clinical research on these diseases.In this paper,the detection and inhibition of tyrosinase and their application in whitening products are reviewed,with special emphasis on development of fluorescent probes and inhibitors.Hopefully,this review will help design more efficient and sensitive tyrosinase probes and inhibitors,as well as shed light on novel treatment of diseases such as melanoma.展开更多
The determination method of catechol by fluorescence quenching was developed.The assay was based on the combination of the unique property of gold nanoparticles with tyrosinase enzymatic reaction.In the presence of ty...The determination method of catechol by fluorescence quenching was developed.The assay was based on the combination of the unique property of gold nanoparticles with tyrosinase enzymatic reaction.In the presence of tyrosinase,the fluorescence of gold nanoparticles was quenched by catechol which can be employed to detect catechol.Under the optimal conditions,a linear range 5.0×10^(-7)-1.0×10^(-3) mol L^(-1) and a detection limit 1.0×10^(-7) mol L^(-1) of catechol were obtained.o-Quinone intermediate produced...展开更多
Tyrosinase exists universally in organisms and is a characteristic enzyme of melanocytes. Tyrosinase family genes in vertebrates consist of 3 related members; tyrosinase （TYR, Tyr）, tyro sinase-related protein-1 （T...Tyrosinase exists universally in organisms and is a characteristic enzyme of melanocytes. Tyrosinase family genes in vertebrates consist of 3 related members; tyrosinase （TYR, Tyr）, tyro sinase-related protein-1 （TRP-1, Tyrp 1）, and tyro sinase-related protein-2 （TRP-2, Tyrp2, Dct）. These proteins catalyze melanin biosynthesis in pigment cells and play important roles in determining vertebrate coloration. Transcription of the TYR and TRP genes is useful for studying neural crest and optic vesicle cell migration and differentiation during emblyogenesis and important in pigment rescue in fish. In this paper, the structure of gene and protein molecular evolution, function and roles of the TYR family in fish were reviewed.展开更多
The present study modified potato protein and flour with tyrosinase to promote the diversification of potato staple foods.The results indicated that tyrosinase treatment markedly altered the secondary structure of pro...The present study modified potato protein and flour with tyrosinase to promote the diversification of potato staple foods.The results indicated that tyrosinase treatment markedly altered the secondary structure of proteins.After tyrosinase treatment,the maximum decomposition temperature of potato protein and flour increased from 322.32 to 332.40℃ and from 294.24 to 299.61℃,respectively.Tyrosinase treatment remarkably reduced the pasting viscosity of potato flour,that is,the peak viscosity,through reducing viscosity,breakdown,final viscosity,and setback by 32.50,60.98,13.04,68.24,and 74.31%,respectively.In contrast,tyrosinase treatment increased the shear resistance and hardness of the protein and flour gels;the maximum stress values of the protein and flour gels increased from 1.48 to 10.1% and from 6.87 to 14.8%,respectively.Furthermore,tyrosinase treatment promoted viscoelastic properties and structural stability of potato protein and flour.These results may provide an important foundation for the development of novel potato staple foods.展开更多
Objective:To find out and compare the in vitro antioxidant and tyrosinase inhibitory activities of two species of mangrove plants.Methods:Mangrove samples were harvested at the shoreline on the island of Weno,Chuuk St...Objective:To find out and compare the in vitro antioxidant and tyrosinase inhibitory activities of two species of mangrove plants.Methods:Mangrove samples were harvested at the shoreline on the island of Weno,Chuuk State in Micronesia.The phenol content,antioxidant activity(based on DPPH-free radical scavenging)and tyrosinase inhibitory activity in different tissues(leaves,barks and roots)of Rhizophora stylosa(R.stylosa)and Sonneratia alba(S.alba),collected from the island of Weno.Results:Total phenol content ranged from 4.87 to 11.96 mg per g of freeze dried samples.The highest antioxidant activity was observed in R.styiosa bark(85.5%).The highest tyrosinase inhibitory activity was found in S.alba bark.Also,total phenol content and antioxidant activity were higher in methanol extracts than in aqueous extracts.Conclusions:Taken together,the results of this study proved that mangroves can be excellent sources of antioxidant compounds.展开更多
A mixed self-assembled monolayers （SAMs） of thioctic acid （T-COOH） and thioctic acid amide （T-NH2） were used to immobilize tyrosinase for fabricating biosensor. The results showed that the mixed SAMs prepared fr...A mixed self-assembled monolayers （SAMs） of thioctic acid （T-COOH） and thioctic acid amide （T-NH2） were used to immobilize tyrosinase for fabricating biosensor. The results showed that the mixed SAMs prepared from solution at the ratio of 1：4 provided an excellent microenvironment for enzymatic reaction between tyrosinase and substrate. The biosensor exhibited a fast response and high sensitivity for sensing substrate.展开更多
Two new 24-methyl lanostane triterpenoids,hispindic acids A and B（1 and 2）,and a new phenolic compound,hispinine（7）,along with nine known compounds（3-6,and 8-12）,were isolated from the fruiting bodies of Inonotu...Two new 24-methyl lanostane triterpenoids,hispindic acids A and B（1 and 2）,and a new phenolic compound,hispinine（7）,along with nine known compounds（3-6,and 8-12）,were isolated from the fruiting bodies of Inonotus hispidus.Their structures were elucidated based on the extensive analysis of spectroscopic data（NMR and HRMS）.Hispindic acid A（1） possesses an unusual formyl group at C-30.Compounds 1,3-4,and 8 showed stronger activate abilities of melanogenesis and tyrosinase in B16 melanoma cells than those of positive control,8-methoxypsoralen,at 50 μmol/L展开更多
Phenolic compounds such as chlorogenic acid,cryptochlorogenic acid,neochlorogenic acid and caffeic acid are widely distributed in fruits,vegetables and traditional Chinese medicines with a wide range of biological act...Phenolic compounds such as chlorogenic acid,cryptochlorogenic acid,neochlorogenic acid and caffeic acid are widely distributed in fruits,vegetables and traditional Chinese medicines with a wide range of biological activities.Tyrosinase plays a critical role in the food industry,but recent studies have proposed unexplored aspects of clinical application.Tyrosinase-catalyzed oxidation of four polyphenols as well as its underlying mechanism remains unclear.In the current work,we investigated the kinetic properties of tyrosinase-catalyzed oxidation of the four polyphenols of interest.To measure the unstable o-quinone products,an analytical method using 3-methyl-2-benzothiazolinone hydrazone(MBTH)was established.The optimal incubation time,buffer pH,temperature and enzyme concentration for the enzyme activity in the presence of each polyphenol of interest were investigated.Under the final optimized conditions,the kinetics and substrate specificity of four polyphenols were examined.K inetic data showed that tyrosinase had the greatest substrate affinity to chlorogenic acid compared with its isomers and caffeic acid.The catalytic efficiency with chlorogenic acid was 8-to 15-fold higher than that with the other 3 polyphenols.Molecular docking study demonstrated that the tight binding of chlorogenic acid at the peripheral site should be the major reason for the specificity to chlorogenic acid.In light of this,the rational design of high-affinity inhibitors against tyrosinase may focus on the binding of both the Cu site and peripheral site.This study will supply a basis for the selection of phenolic acids in food industry and health carc.展开更多
Time-temperature indicators(TTIs) are convenient intuitive devices that are widely used to predict food quality. The aim of this study is to develop a new simple device which can be attached to food packages as a qual...Time-temperature indicators(TTIs) are convenient intuitive devices that are widely used to predict food quality. The aim of this study is to develop a new simple device which can be attached to food packages as a quality indicator for turbot sashimi. In this study, a solid TTI based on the reaction between tyrosinase and tyrosine was developed. The Arrhenius behavior of this enzymatic TTI was studied. The kinetics of the tyrosinase-based TTI was investigated in the form of color change from colorless to dark black induced by the enzymatic reaction. The mathematical formula for the color alterations as a function of time and temperature was established. The longest indication time for the developed TTI was 50 hours at 4℃. The activation energy of the tyrosinase-based TTI was 0.409 k J mol^(-1). The suitability of the tyrosinase-based TTI was validated for turbot sashimi using total plate count. The feasibility of using this TTI as a quality indicator for turbot sashimi was assessed based on the activation energy and indication time. Therefore, the tyrosinasebased TTI system developed in this study could be used as an effective tool for monitoring the quality changes of turbot sashimi during the distribution and storage.展开更多
Tyrosinase inhibitory activity of the extractives from A. cathartica was examined and their new bioactivity and potent active compounds were identified. Five compounds, glabridin, new lignan, kaempferol, naringenin, a...Tyrosinase inhibitory activity of the extractives from A. cathartica was examined and their new bioactivity and potent active compounds were identified. Five compounds, glabridin, new lignan, kaempferol, naringenin, and allamandicin, were isolated by a series of chromatography, and identified by NMR and LC-MS. Among them, glabridin had the high-est tyrosinase inhibitory activity (IC50:2.93 μM) which is 15 times stronger than that of kojic acid used as positive con-trol (IC50:43.7 μM). Moreover the lignan was indentified as 1-[3-(4-allyl-2,6-dimethoxyphenoxy)-4-methoxyphenyl] propane-1,2,diol which was a novel lignan.展开更多
文摘Objective:Tyrosinase is the rate-limiting enzyme in the generation of melanin.The feline tyrosinase mutation,G302R,confers temperature-sensitive loss of function,resulting in the familiar Siamese cat phenotype.Crystal or cryoEM structures are elusive for any mammalian tyrosinase to date.Protein misfolding is suggested as a basis for phenotypes resulting frommutant tyrosinases,but this hypothesis needs structural confirmation.Our objective for this study is to confirm misfolding of mutant tyrosinase as a basis for temperature-sensitive phenotypes compared to catalytic dysfunction that may be responsible for other tyrosinase mutant breed phenotypes.Methods:We have employed AlphaFold3 to compare structural alignments of four well-characterized feline tyrosinase mutations to wild type(WT)feline tyrosinase;SiameseG302R,Burmese G227W,Mocha delI274-L312+2aa,andAlbino del401-529 lacking the transmembrane and C-terminus domains.Results:The manifestations of the bulkier side chains of the Siamese positively charged arginine(R)and the Burmese hydrophobic tryptophan(W)are evident locally.But interestingly,the major differences between the structures lie in the usually ignored signal peptide(SP)regions of each mutant.As the maturation of the nascent tyrosinase peptide is highly dependent on accurate and early cleavage of the SP,we hypothesize these structural anomaliesmay formthe basis formisfolded or truncated final enzyme forms,leading to the observed phenotypes seen in these cats.Conclusions:We have identified enzyme dysfunction and protein misfolding as separate mechanisms for feline coat phenotypes resulting from tyrosinase mutations.
文摘Pimenta dioica is a tropical Caribbean tree belonging to the family Myrtaceae,widely used in various human activities,including perfume production,food flavoring,natural pesticides,and medicine.This study aimed to explore the chemical composition of Pimenta dioica flower essential oil obtained via hydrodistillation using GC-MS analysis.Additionally,the oil’s tyrosinase inhibitory activity was investigated.The effectiveness of the oil’s major constituents in binding to tyrosinase was also evaluated through molecular docking simulations.GC-MS analysis identified fifteen compounds,with eugenol(70.59%)as the major component,followed byβ-myrcene(10.54%),limonene(8.55%),β-ocimene(4.92%),α-phellandrene(1.39%),and linalool(1.46%).The oil exhibited tyrosinase inhibitory activity with an IC_(50) value of 28.65±0.77μg/mL,compared to kojic acid(IC_(50)=1.94±0.53μg/mL).It also showed moderate antioxidant activity with an IC_(50) of 5.41±0.68μg/mL,relative to quercitrin(0.78±0.37μg/mL).Molecular docking studies revealed that the six identified constituents exhibited good binding affinity and fitting to the tyrosinase active site,as indicated by docking scores and specific interactions.These interactions likely contribute to the overall inhibitory effect through multiple binding modes.The findings suggest that the monoterpene content plays a crucial role in the observed inhibitory activity and enhance our understanding of natural compounds as potential therapeutics for tyrosinase-related disorders.Therefore,P.dioica flower essential oil may represent a safe and effective natural source of skin-whitening agents for cosmetic and pharmaceutical applications.Further investigations,including in vivo studies,pharmacokinetics,pharmacodynamics,and toxicity profiling,are recommended.
文摘[Objective] The paper was to study the activity of tyrosinase,so as to provide reference for preventing browning of potatoes as well as fruits and vegetables containing tyrosinase.[Method] With potato as raw material and Na2HPO4-HCl in buffer solution（pH=7.2）as system,spectrophotometer was used to measure the absorbance of potato extract at 480nm,the curve was established,and the activity of tyrosinase was obtained.[Result] The changes of data were little under the above conditions,and the stability of tyrosinase activity was high.[Conclusion] Using spectrophotometry to determine the tyrosinase activity in potato is simple with high accuracy.
基金Supported by National Natural Science Foundation of China(3117207430700071)National Natural Science Foundation of Shandong Province(ZR2010CL002)~~
文摘[Objective] This study aimed to analyze tyrosinase activity and its expression in Varicorhinus macrolepis. [Method] V. macrolepis was used as experimental material for the analysis and research of tyrosinase in nine kinds of organs and tissues of male and female V. macrolepis individuals by using polyacrylamide gel electrophoresis and biochemical staining method, spectrophotometry and enzyme histochemical technology. [Result] Tyrosinase exists in the liver and pancreas, intestine and spleen of female and male V. macrolepis and in the gallbladder of male V. macrolepis. Tyrosinase activities in various tissues of V. macrolepis varied largely. Specifically, tyrosinase activities in the spleen was the maximum, which was higher in female V. macrolepis than in males. According to the enzyme histochemistry results, strong positive signals of tyrosinase existed in the spleen, intestine, liver and pancreas and gallbladder of V. macrolepis, which was the strongest in the spleen. [Conclusion] In this paper, research on tissue localization of tyrosinase in V. macrolepis had been first reported, which provided theoretical basis for further exploring the functions of tyrosinase in V. macrolepis.
文摘Objective] Tyrosinase is a kind of polyphenol oxidase used widely, and the study of tyrosinase attracts extensive attention. [Method] ln this experiment, A conversion kinetic curve of dopa solution was obtained using absorbance of potato extract at 480 nm in Na2HPO4-HCl buffer system at a pH value of 7.2 with the vari-ation rate of absorbance against time （ΔA/Δt） as reaction rate, and the activity of tyrosinase could thus be calculated. [Result] The results showed that at the wave-length, in the Na2HPO4-HCl buffer system with a pH value at 7.2, there was little in-terference to the system, the data showed smal fluctuations, and the activity of ty-rosinase was high and stable, further providing a theoretical foundation for the de-termination and study of factors influencing tyrosinase activity. [Conclusion] The catalytic activity of tyrosinase was studied and determined with buffer solution as substrate with high accuracy and good effect.
基金National Key Technology R&D Program of China (Grant No.2007BAI27B05).
文摘Four series of derivatives of vanillin,anisaldehyde,genistein and aloe emodin were prepared.The single crystal of （E）-1-（5-（4-methoxyphenyl）-3-（4-methoxystyryl）-4,5-dihydro-1H-pyrazol-1-yl）ethanone,which was synthesized from vanillin, was obtained by spontaneous evaporation method.All the compounds were tested for the tyrosinase inhibitory activities.The results demonstrated that the IC_（50）values of vanillin,anisaldehyde,genistein and aloe emodin against mushroom tyrosinase activity are 68,49,343 and 160μM,respectively.Among the twelve derivatives,（E）-1-（5-（4-methoxyphenyl）-3-（4-methoxystyryl）-4,5- dihydro-1H-pyrazol-1-yl）ethanone from vanillin and 4,5-dimethoxy-9,10-dioxo-9,10-dihydroanthracene-2-carboxylic acid from aloe emodin showed good inhibition against the tyrosinase with IC_（50）values of 18μM and 21μM,respectively.
基金Supported by the Natural Science Foundation of Guangdong Province (No. 011563, No. 04020114).
文摘The inhibitory effect of ferulic acid on the diphenolase activity of mushroom tyrosinase and the kinetic behavior were studied with L-3,4-dihydroxyphenylalanine （L-DOPA） as substrate. The inhibitor concentration leading to 50% relative activity lost （IC50） was estimated to be 0.15 mmol·L^-1. The inhibition mechanism obtained from Lineweaver-Burk plots shows that ferulic acid is a competitive inhibitor and the inhibition of tyrosinase by ferulic acid is a reversible reaction. The equilibrium constant for ferulic acid binding with the tyrosinase was determined to be 0.25 mmol·L^-1 for diphenolase. Keywords tyrosinase, ferulic acid, kinetics, inhibition, L-DOPA, diphenolase
基金Supported by the Next-Generation BioGreen 21 Program,Rural Development Administration,Republic of Korea,Grant No.PJ009583002013
文摘Objective:To investigate the suitability of citrus-press cakes,by-products of the juice industry as a source for the whitening agents for cosmetic industry.Methods:Ethylacetate extracts of citrus-press cakes(CCE)were examined for their anti-melanogenic potentials in terms of the inhibition of melanin production and mechanisim of melanogenesis by using Western Blot analysis with tyrosinese,tyrosinase-related protein-1(TRP-1),TRP2,and microphthalmia-associated transcription factor(MITF)proteins.To apply the topical agents,citrus-press cakes was investigated the safety in human skin cell line.Finally flavonoid analysis of CCE was also determined by HPLC analysis.Results:Results indicated that CCE were shown to down-regulate melanin content in a dose-dependent pattern.The CCE inhibited tyrosinase,TRP-2,and MITF expressions in a dose-dependent manner.To test the applicability of CCE to human skin,we used MTT assay to assess the cytotoxic effects of CCE on human keratinocyte HaCaT cells.The CCE exhibited low cytotoxicity at 50μg/mL.Characterization of the citrus-press cakes for flavonoid contents using HPLC showed varied quantity of rutin,narirutin,and hesperidin.Conclusions:Considering the anti-melanogenic activity and human safety,CCE is considered as a potential anti-melanogenic agent and may be effective for topical application for treating hyperpigmentation disorders.
基金This project was supported financially by the Yunnan Provincial Science and Technology Department(Nos.2017ZF003-04,2015HB093 and 2019HA001).Authors are grateful to the staff of the analytical group of the State Key Laboratory of Phytochemistry and Plant Resources in West China,Kunming Institute of Botany,Chinese Academy of Sciences,for measurements of all spectra.
文摘Aqueous ethanol extracts of powdered stems of Dendrobium loddigesii afforded three new phenolics including threo-7-Oethyl-9-O-(4-hydroxyphenyl)propionyl-guaiacylglycerol(1),(R)-4,5,4ʹ-trihydroxy-3,3ʹ,α-trimethoxybibenzyl(2)and(S)-5,5′,7-trihydroxy-3′,4′-dimethoxyflavanone(3),together with eleven known analogues.Their structures were determined by extensive spectroscopic analysis.To identify natural antioxidants,whitening,and anti-aging agents,the abilities of these phenolics were assessed to scavenge the 1,2-diphenyl-2-picrylhydrazyl(DPPH)radical,their abilities to inhibit tyrosinase production,and their abilities to stimulate collagen production by human dermal fibroblasts-adult(HDFa)assay.It was found that compounds 1,4-8,13 and 14 exhibited significant DPPH radical scavenging activities,compound 10 exhibited tyrosinase inhibitory activity(IC_(50)37.904μg/mL),and compound 9 showed significant collagen production with an EC_(50)value of 3.182μg/mL.These results suggest that phenolic constituents from D.loddigesii may be candidate antioxidants,skin-whitening and/or anti-aging agents.
基金This work was financially supported by the National Natural Science Foundation of China(81672508,21675085)Jiangsu Provincial Foundation for Distinguished Young Scholars(BK20170041,BK20170042)+5 种基金the Joint Research Funds of Department of Science&Technology of Shaanxi Province and Northwestern Polytechnical University(2020GXLH-Z-008,2020GXLH-Z-023)the Natural Science Basic Research Programof Shaanxi(Program No.2019JM-016)Key Research and Development Program of Shaanxi(2020ZDLGY13-04)Open Research Fund of Anhui Key Laboratory of Tobacco Chemistry(20181140)China-Sweden Joint Mobility Project(51811530018)Fundamental Research Funds for the Central Universities.
文摘Tyrosinase is an important enzyme in controlling the formation of melanin in melanosome,and plays a key role in the pigmentation of hair and skin.The abnormal expression or activation of tyrosinase is associated with several diseases such as albinism,vitiligo,melanoma and Parkinson disease.Excessive deposition of melanin could cause diseases such as freckles and brown spots in the human body,and it is also closely related to browning of fruits and vegetables and insect molting.Detecting and inhibiting the activity of tyrosinase is of extraordinary value in the progress of diagnosis and treatment of these diseases.Therefore,many selective optical detection probes and small molecular inhibitors have been developed,and have made significant contributions to the basic and clinical research on these diseases.In this paper,the detection and inhibition of tyrosinase and their application in whitening products are reviewed,with special emphasis on development of fluorescent probes and inhibitors.Hopefully,this review will help design more efficient and sensitive tyrosinase probes and inhibitors,as well as shed light on novel treatment of diseases such as melanoma.
基金supported by the National Natural Science Foundation of China(No.20875059)
文摘The determination method of catechol by fluorescence quenching was developed.The assay was based on the combination of the unique property of gold nanoparticles with tyrosinase enzymatic reaction.In the presence of tyrosinase,the fluorescence of gold nanoparticles was quenched by catechol which can be employed to detect catechol.Under the optimal conditions,a linear range 5.0×10^(-7)-1.0×10^(-3) mol L^(-1) and a detection limit 1.0×10^(-7) mol L^(-1) of catechol were obtained.o-Quinone intermediate produced...
文摘Tyrosinase exists universally in organisms and is a characteristic enzyme of melanocytes. Tyrosinase family genes in vertebrates consist of 3 related members; tyrosinase （TYR, Tyr）, tyro sinase-related protein-1 （TRP-1, Tyrp 1）, and tyro sinase-related protein-2 （TRP-2, Tyrp2, Dct）. These proteins catalyze melanin biosynthesis in pigment cells and play important roles in determining vertebrate coloration. Transcription of the TYR and TRP genes is useful for studying neural crest and optic vesicle cell migration and differentiation during emblyogenesis and important in pigment rescue in fish. In this paper, the structure of gene and protein molecular evolution, function and roles of the TYR family in fish were reviewed.
基金supported by the National Natural Science Foundation of China(31771933 and 31471700)the Shandong Key Research and Development Plan(Public Welfare Projects),China(2019GSF109035)+2 种基金the International Cooperation Foundation of Qilu University of Technology(Shandong Academy of Sciences),China(QLUTGJUZ014)the Special Funds for Taishan Scholars Project,China(ts201712060)the Independent Training Innovation Team Project of China(2018GXRC004)。
文摘The present study modified potato protein and flour with tyrosinase to promote the diversification of potato staple foods.The results indicated that tyrosinase treatment markedly altered the secondary structure of proteins.After tyrosinase treatment,the maximum decomposition temperature of potato protein and flour increased from 322.32 to 332.40℃ and from 294.24 to 299.61℃,respectively.Tyrosinase treatment remarkably reduced the pasting viscosity of potato flour,that is,the peak viscosity,through reducing viscosity,breakdown,final viscosity,and setback by 32.50,60.98,13.04,68.24,and 74.31%,respectively.In contrast,tyrosinase treatment increased the shear resistance and hardness of the protein and flour gels;the maximum stress values of the protein and flour gels increased from 1.48 to 10.1% and from 6.87 to 14.8%,respectively.Furthermore,tyrosinase treatment promoted viscoelastic properties and structural stability of potato protein and flour.These results may provide an important foundation for the development of novel potato staple foods.
基金supported by Korea Institute of Ocean Science&Technology research project:E99161
文摘Objective:To find out and compare the in vitro antioxidant and tyrosinase inhibitory activities of two species of mangrove plants.Methods:Mangrove samples were harvested at the shoreline on the island of Weno,Chuuk State in Micronesia.The phenol content,antioxidant activity(based on DPPH-free radical scavenging)and tyrosinase inhibitory activity in different tissues(leaves,barks and roots)of Rhizophora stylosa(R.stylosa)and Sonneratia alba(S.alba),collected from the island of Weno.Results:Total phenol content ranged from 4.87 to 11.96 mg per g of freeze dried samples.The highest antioxidant activity was observed in R.styiosa bark(85.5%).The highest tyrosinase inhibitory activity was found in S.alba bark.Also,total phenol content and antioxidant activity were higher in methanol extracts than in aqueous extracts.Conclusions:Taken together,the results of this study proved that mangroves can be excellent sources of antioxidant compounds.
基金financially supported by the Scientific Research Foundation of State Education Ministry of China (Jiaowaisiliu[2008]890)Research Foundation of Education Department of Hebei Province of China(No. 2007132)
文摘A mixed self-assembled monolayers （SAMs） of thioctic acid （T-COOH） and thioctic acid amide （T-NH2） were used to immobilize tyrosinase for fabricating biosensor. The results showed that the mixed SAMs prepared from solution at the ratio of 1：4 provided an excellent microenvironment for enzymatic reaction between tyrosinase and substrate. The biosensor exhibited a fast response and high sensitivity for sensing substrate.
基金supported by the Recruitment Program of Global Experts(to Tao Yuan),Chinathe Xinjiang Key Research and Development Program(No.2016B03038-3)
文摘Two new 24-methyl lanostane triterpenoids,hispindic acids A and B（1 and 2）,and a new phenolic compound,hispinine（7）,along with nine known compounds（3-6,and 8-12）,were isolated from the fruiting bodies of Inonotus hispidus.Their structures were elucidated based on the extensive analysis of spectroscopic data（NMR and HRMS）.Hispindic acid A（1） possesses an unusual formyl group at C-30.Compounds 1,3-4,and 8 showed stronger activate abilities of melanogenesis and tyrosinase in B16 melanoma cells than those of positive control,8-methoxypsoralen,at 50 μmol/L
基金The study was supported by grants from the National Natural Science Foundation of China(No.81773811)Yunnan Applied Basic Research Project(No.2017FB074)+1 种基金the Yunnan Provincial Tobacco Monopoly Bureau Grants(No.2017YN09)the Fundamental Research Funds for the Central Universities(No.2020kfyXGYJ061).
文摘Phenolic compounds such as chlorogenic acid,cryptochlorogenic acid,neochlorogenic acid and caffeic acid are widely distributed in fruits,vegetables and traditional Chinese medicines with a wide range of biological activities.Tyrosinase plays a critical role in the food industry,but recent studies have proposed unexplored aspects of clinical application.Tyrosinase-catalyzed oxidation of four polyphenols as well as its underlying mechanism remains unclear.In the current work,we investigated the kinetic properties of tyrosinase-catalyzed oxidation of the four polyphenols of interest.To measure the unstable o-quinone products,an analytical method using 3-methyl-2-benzothiazolinone hydrazone(MBTH)was established.The optimal incubation time,buffer pH,temperature and enzyme concentration for the enzyme activity in the presence of each polyphenol of interest were investigated.Under the final optimized conditions,the kinetics and substrate specificity of four polyphenols were examined.K inetic data showed that tyrosinase had the greatest substrate affinity to chlorogenic acid compared with its isomers and caffeic acid.The catalytic efficiency with chlorogenic acid was 8-to 15-fold higher than that with the other 3 polyphenols.Molecular docking study demonstrated that the tight binding of chlorogenic acid at the peripheral site should be the major reason for the specificity to chlorogenic acid.In light of this,the rational design of high-affinity inhibitors against tyrosinase may focus on the binding of both the Cu site and peripheral site.This study will supply a basis for the selection of phenolic acids in food industry and health carc.
基金the Science and Technology Major Projects of Shandong Province (No. 2015ZDZX05 003)the National Science & Technology Pillar Program (No. 2015BAD16B0902)
文摘Time-temperature indicators(TTIs) are convenient intuitive devices that are widely used to predict food quality. The aim of this study is to develop a new simple device which can be attached to food packages as a quality indicator for turbot sashimi. In this study, a solid TTI based on the reaction between tyrosinase and tyrosine was developed. The Arrhenius behavior of this enzymatic TTI was studied. The kinetics of the tyrosinase-based TTI was investigated in the form of color change from colorless to dark black induced by the enzymatic reaction. The mathematical formula for the color alterations as a function of time and temperature was established. The longest indication time for the developed TTI was 50 hours at 4℃. The activation energy of the tyrosinase-based TTI was 0.409 k J mol^(-1). The suitability of the tyrosinase-based TTI was validated for turbot sashimi using total plate count. The feasibility of using this TTI as a quality indicator for turbot sashimi was assessed based on the activation energy and indication time. Therefore, the tyrosinasebased TTI system developed in this study could be used as an effective tool for monitoring the quality changes of turbot sashimi during the distribution and storage.
文摘Tyrosinase inhibitory activity of the extractives from A. cathartica was examined and their new bioactivity and potent active compounds were identified. Five compounds, glabridin, new lignan, kaempferol, naringenin, and allamandicin, were isolated by a series of chromatography, and identified by NMR and LC-MS. Among them, glabridin had the high-est tyrosinase inhibitory activity (IC50:2.93 μM) which is 15 times stronger than that of kojic acid used as positive con-trol (IC50:43.7 μM). Moreover the lignan was indentified as 1-[3-(4-allyl-2,6-dimethoxyphenoxy)-4-methoxyphenyl] propane-1,2,diol which was a novel lignan.
