【摘要】 蓖麻蚕Philosamta cynthia ?n,高度提纯的中肠γ-谷氨酰转肽酶（γ-GTP）体外转肽作用表明:L-苯丙氨酸、L-甲硫氨酸,L-半胱氨酸、L-色氨酸,L-精氨酸和L-赖氨酸是最好的γ-谷氨酰的受体,而L-谷氨酸和L-谷氨酰胺（L-Gln）系该酶良好的γ-谷氨酰供体。酶对γ-谷氨酰对硝基苯胺（γ-GNA）的K_m为0.13mmol/L（含L-苯丙氨酸）和0.29mmol/L（无L-苯丙氨酸）。谷胱甘肽（GSH）和L-Gln与γ-GNA竞争酶的γ-谷氨酰结合部位,其抑制常数K₁值分别为0.5mmol/L和1.1mmol/L。γ-GTP催化L-Gln的酰胺键水解和转肽,其催化速率相当于对γ-GNA的38％。更多还原

【Abstract】 The highly purified γ-glutamyltranspeptidase preparation from the mid-gut of eri-siikworm Philosamia cynthia ricini was examined with respect to its specificty toward different γ-glu-tnmyl donors and acceptors. Of the 20 ainino acids tested, phenylalanine, methionine, cystine, tryptophene, arginine and lysine were the best acceptors of the γ-glutamyl group,whereas glutamine and glutamate bound effectively to the γ-glutamyl binding site. The K values for γ-glutamyl-p-nitroaniline are 0.13 mmoI/L with phenylalanine and 0.29 mmol /L without phenylalanine. The competitive inhibition constant K1 values for glutathione and gluiamine are 0.5 and 1.1 mmol/L respectively in the presence of phenylalanine. The enzyme catalyzes, the utilization of glutamine by conversion to glutamate, ammonia and γ-glutamyl-L-amino acids at about 38% of the rate observed for catalysis of releasing p-nitroaniline from γ-glutamyl-p-nitroani-line. The participation of the enzyme in the absorption and transportation of some indispensable ami no acids in the mid-gut of the silkworm is discussed.更多还原