As a lipid with significant nutritional and health benefits,structured triacylglycerols(STAGs)are currently synthesized via enzymatic method.However,the application of STAGs is limited by the availability and characte...As a lipid with significant nutritional and health benefits,structured triacylglycerols(STAGs)are currently synthesized via enzymatic method.However,the application of STAGs is limited by the availability and characteristics of raw materials.This study presents a novel approach for producing STAGs by reconfiguring triacylglycerol pathway in Saccharomyces cerevisiae.The substrate preference of acyltransferases involved in triacylglycerol pathway was elucidated through analysis of the acyl distribution in recombinants overexpressing or deleting acyltransferase.To synthesize 1,3-oleic acid-2-palmitic acid triacylglycerol(OPO-TAG),fatty acid profiles were modulated by overexpressing mutated ACC1S659A,S1157A and replacing the native fatty acid desaturase Ole1p with heterologous ChDes9-2,resulting in C18:1 and C16:0 contents of 49%(v/v)and 16%(v/v),respectively.Deletion of DGA1 and TGL3/4/5 enabled the recombinant to produce OPO-TAG with a maximum content of 45.4%(mol/mol).Under optimized conditions,the OPO-TAG titer reached 32.1 mg/L,approximately 100-fold higher than that of the original strain.Feeding experiments demonstrated the feasibility of harnessing specific acyltransferases to synthesis 1,3-medium chain-2-long chain TAGs and TAGs enriched in eicosapentaenoic acid.This work not only provides valuable insights into the enzymatic regulation of triacylglycerol synthesis,but also establishes a sustainable yeast-based system for the production of STAGs.展开更多
Due to their significant value in both economy and ecology,Daphnia had long been employed to investigate in vivo response of cholinesterase(ChE) in anticholinesterase exposures,whereas the type constitution and proper...Due to their significant value in both economy and ecology,Daphnia had long been employed to investigate in vivo response of cholinesterase(ChE) in anticholinesterase exposures,whereas the type constitution and property of the enzyme remained unclear.A type of ChE was purified from Daphnia magna using a three-step procedure,i.e.,Triton X-100 extraction,ammonium sulfate precipitation,and diethylaminoethyl(DEAE)-Sepharose Fast-Flow chromatography.According to sodium dodecyl sulfate polyacrylamide gel electrophoresis(SDS-PAGE),molecular mass of the purified ChE was estimated to be 84 kDa.Based on substrate studies,the purified enzyme preferred butyrylthiocholine iodide(BTCh) [with maximum velocity(Vmax)/Michaelis constant(Km)=8.428 L/(min·mg protein)] to acetylthiocholine iodide(ATCh) [with V max /Km =5.346 L/(min·mg protein)] as its substrate.Activity of the purified enzyme was suppressed by high concentrations of either ATCh or BTCh.Inhibitor studies showed that the purified enzyme was more sensitive towards inhibition by tetraisopropylpyrophosphoramide(iso-OMPA) than by 1,5-bis(4-allyldimethylammoniumphenyl) pentan-3-one dibromide(BW284C51).Result of the study suggested that the purified ChE was more like a type of pseudocholinesterase,and it also suggested that Daphnia magna contained multiple types of ChE in their bodies.展开更多
To understand the effects of sand grain size on habitat selection, we conducted a field study on the steppe toad-headed lizard in Hunshandake Desert northern China. Methods of mark-recapture and transect survey were u...To understand the effects of sand grain size on habitat selection, we conducted a field study on the steppe toad-headed lizard in Hunshandake Desert northern China. Methods of mark-recapture and transect survey were used to investigate the density of steppe toad-headed lizards and the environmental variables. The comparison on lizard densities among the habitats with different environmental factors revealed that： 1） population density of the steppe toad-headed lizard differed significantly among the habitats with different sand grain size indexes（SGSIs, representing roughness of sand substrate）： the highest lizard density was found in the group with an SGSI of 〉 0.30, whereas the lowest density was found in the group with an SGSI of 0–0.15; and 2） vegetation cover, soil moisture, invertebrate diversity index, and abundance had no significant effects on the lizard density. These results implied that the sand grain size was the most important determinant of habitat selection for steppe toad-headed lizards in Hunshandake Desert. Steppe toad-headed lizards could avoid structural habitats that have negative effects on their maximal sprinting capabilities. Considering the changing sand grain size in the development phase of sand dunes, the sand lizard could be used as an indicator of the process of desertification.展开更多
DNA replication elongation is tightly controlled by histone-modifying enzymes.Our previous studies showed that the histone methytransferase TXRl(Tetrahymena Trithorax related protein 1) specifically catalyzes H3K27 mo...DNA replication elongation is tightly controlled by histone-modifying enzymes.Our previous studies showed that the histone methytransferase TXRl(Tetrahymena Trithorax related protein 1) specifically catalyzes H3K27 monomethylation and affects DNA replication elongation in Tetrahymena thermophila.In this study,we investigated whether TXRl has a substrate preference to the canonical H3 over the replacement variant H3.3.We demonstrated by histone mutagenesis that K27 Q mutation in H3.3further aggravated the replication stress phenotype of K27 Q mutation in canonical H3,supporting H3.3 as a physiologically relevant substrate of TXRl.This result is in apparent contrast to the strong preference for canonical H3 recently reported in Arabidopsis homologues ATXR5 and ATXR6,and further corroborates the role of TXRl in DNA replication.展开更多
基金financially supported by grant from the National Natural Science Foundation of China(Grant No.22078013).
文摘As a lipid with significant nutritional and health benefits,structured triacylglycerols(STAGs)are currently synthesized via enzymatic method.However,the application of STAGs is limited by the availability and characteristics of raw materials.This study presents a novel approach for producing STAGs by reconfiguring triacylglycerol pathway in Saccharomyces cerevisiae.The substrate preference of acyltransferases involved in triacylglycerol pathway was elucidated through analysis of the acyl distribution in recombinants overexpressing or deleting acyltransferase.To synthesize 1,3-oleic acid-2-palmitic acid triacylglycerol(OPO-TAG),fatty acid profiles were modulated by overexpressing mutated ACC1S659A,S1157A and replacing the native fatty acid desaturase Ole1p with heterologous ChDes9-2,resulting in C18:1 and C16:0 contents of 49%(v/v)and 16%(v/v),respectively.Deletion of DGA1 and TGL3/4/5 enabled the recombinant to produce OPO-TAG with a maximum content of 45.4%(mol/mol).Under optimized conditions,the OPO-TAG titer reached 32.1 mg/L,approximately 100-fold higher than that of the original strain.Feeding experiments demonstrated the feasibility of harnessing specific acyltransferases to synthesis 1,3-medium chain-2-long chain TAGs and TAGs enriched in eicosapentaenoic acid.This work not only provides valuable insights into the enzymatic regulation of triacylglycerol synthesis,but also establishes a sustainable yeast-based system for the production of STAGs.
基金Project supported by the Zhejiang Provincial Natural Science Foundation of China(No.LY12B07008)the Department of Education of Zhejiang Province,China(No.20070138)
文摘Due to their significant value in both economy and ecology,Daphnia had long been employed to investigate in vivo response of cholinesterase(ChE) in anticholinesterase exposures,whereas the type constitution and property of the enzyme remained unclear.A type of ChE was purified from Daphnia magna using a three-step procedure,i.e.,Triton X-100 extraction,ammonium sulfate precipitation,and diethylaminoethyl(DEAE)-Sepharose Fast-Flow chromatography.According to sodium dodecyl sulfate polyacrylamide gel electrophoresis(SDS-PAGE),molecular mass of the purified ChE was estimated to be 84 kDa.Based on substrate studies,the purified enzyme preferred butyrylthiocholine iodide(BTCh) [with maximum velocity(Vmax)/Michaelis constant(Km)=8.428 L/(min·mg protein)] to acetylthiocholine iodide(ATCh) [with V max /Km =5.346 L/(min·mg protein)] as its substrate.Activity of the purified enzyme was suppressed by high concentrations of either ATCh or BTCh.Inhibitor studies showed that the purified enzyme was more sensitive towards inhibition by tetraisopropylpyrophosphoramide(iso-OMPA) than by 1,5-bis(4-allyldimethylammoniumphenyl) pentan-3-one dibromide(BW284C51).Result of the study suggested that the purified ChE was more like a type of pseudocholinesterase,and it also suggested that Daphnia magna contained multiple types of ChE in their bodies.
基金financial support of the Key Basic Science and Technology Project of the Ministry of Science and Technology, China (2013FY110300)the National Natural Science Foundation of China (No. 31572260)the Knowledge Innovation Project of the Chinese Academy of Sciences (KSCX2-EW-J-2)
文摘To understand the effects of sand grain size on habitat selection, we conducted a field study on the steppe toad-headed lizard in Hunshandake Desert northern China. Methods of mark-recapture and transect survey were used to investigate the density of steppe toad-headed lizards and the environmental variables. The comparison on lizard densities among the habitats with different environmental factors revealed that： 1） population density of the steppe toad-headed lizard differed significantly among the habitats with different sand grain size indexes（SGSIs, representing roughness of sand substrate）： the highest lizard density was found in the group with an SGSI of 〉 0.30, whereas the lowest density was found in the group with an SGSI of 0–0.15; and 2） vegetation cover, soil moisture, invertebrate diversity index, and abundance had no significant effects on the lizard density. These results implied that the sand grain size was the most important determinant of habitat selection for steppe toad-headed lizards in Hunshandake Desert. Steppe toad-headed lizards could avoid structural habitats that have negative effects on their maximal sprinting capabilities. Considering the changing sand grain size in the development phase of sand dunes, the sand lizard could be used as an indicator of the process of desertification.
基金supported by the Natural Science Foundation of China (31470064,31522051 to Shan Gao)the National Institutes of Health(R01GM087343 to Yifan Liu)+1 种基金AoShan Talents Program supported by Qingdao National Laboratory for Marine Science and Technology(2015ASTP)China and a research grant by Qingdao government(15-12-1-1-jch)
文摘DNA replication elongation is tightly controlled by histone-modifying enzymes.Our previous studies showed that the histone methytransferase TXRl(Tetrahymena Trithorax related protein 1) specifically catalyzes H3K27 monomethylation and affects DNA replication elongation in Tetrahymena thermophila.In this study,we investigated whether TXRl has a substrate preference to the canonical H3 over the replacement variant H3.3.We demonstrated by histone mutagenesis that K27 Q mutation in H3.3further aggravated the replication stress phenotype of K27 Q mutation in canonical H3,supporting H3.3 as a physiologically relevant substrate of TXRl.This result is in apparent contrast to the strong preference for canonical H3 recently reported in Arabidopsis homologues ATXR5 and ATXR6,and further corroborates the role of TXRl in DNA replication.
