摘要
α-半乳糖苷酶作用于棉子糖后产物为半乳糖和蔗糖,作用于蜜二糖后产物为半乳糖和葡萄糖。对蜜二糖,棉子糖及水苏四糖的水解速率顺序为:蜜二糖(82.2%)>水苏四糖(13.7%)>棉子糖(7.5%)。对于酶的不同底物pNpGal、蜜二糖、棉子糖及α-甲基-D-半乳糖苷,其K_m值分别为0.29、5.0、79.4及55.5mmol/L,V_(max)值分别为1.43、0.23、0.21及0.16μmol·min^(-1)·ml^(-1)。测定了43种碳水化合物对酶活力的影响。其中半乳糖、甘油醛及纤维二糖使酶活力下降50%以上,D-阿拉伯糖、塔格糖、半乳糖醛酸、D-核糖、L-阿拉伯糖、D-葡萄糖酸内酯,乳糖及蔗糖使酶活下降到70%左右;而二羟丙酮、2-脱氧-D-半乳糖及异丙基β-D-硫代半乳糖苷使酶活提高50%左右;其余的碳水化合物对酶活无明显影响。测定了Hg^(2+)、甘油醛及半乳糖对酶的抑制类型。结果表明,Hg^(2+)是α-半乳糖苷酶的非竞争性抑制剂,半乳糖及甘油醛是酶的竞争性抑制剂,后两者的K_i值分别为8.3及12.5mmol/L。
When melibiose or raffinose was incubated with the purified α-galactosidase on paper chromatogram it showed that the degradation products of the former were galactose and glucose, and the later sucrose and galactose.
From the results obtained from the substrates tested, the order of the α-galactosidase relative hydrolysis rate appeared as: melibiose (82.2%)>stachyose(13.7%)>raffinose(7.5%).
The K_m values of the α-galactosidase were 0.29, 5.00, 79.4 and 55.5 mmol/L with the values of V_(max) 1.43, 0.23, 0.21, 0.16 μmol·min^(-1). ml^(-1) for pNPGal, melibiose, raffinose, and α-met-D-galactose respectively.
The effects of 43 kinds of sugars and related compounds on the activity of α-galactosidase have been investigated. Among thus compound, galactose, DL-glyceraldehyde, Darabinose, galacturonic acid, D-ribose, L-arabinose, tagatose, D-gluconolactone, lactose and sucrose exhibiting inhibiting effect with relative activity of 47—70%. Dihydroxy-acetone, isopropyl-β-D-thiogalactopyranoside, 2-deoxy-D-galactose enhanced the activity of the enzyme. The remaining compound other than mentioned above showed no effect at all.
The inhibition model of some compound for α-galactosidase have been investigated. It showed that the galactose and DL-glyceraldehyde acted as competitive inhibitors with K_1 values of 8.3 and 12.5 mmol/L respectively. The Hg^(2+) ion acted as noncompetitive inhibitor.
出处
《微生物学报》
CAS
CSCD
北大核心
1989年第5期337-342,共6页
Acta Microbiologica Sinica
基金
国家自然科学基金
