Repetto Y, Letelier M E, Aldunate J, Morello A
Comp Biochem Physiol B. 1987;87(1):73-8. doi: 10.1016/0305-0491(87)90472-x.
Trypanosoma cruzi epimastigotes show gamma-glutamyltranspeptidase activity which has characteristics significantly different than the mammalian enzyme. The protozoan enzyme is localized in the cytosolic fraction, it has a Km of 1.6 mM and a Vmax of 17.4 nmol/min/mg protein with L-gamma-glutamyl-p-nitroanilide as gamma-glutamyl donor, and an optimun pH range from 7.5 to 8.0. The best amino acid acceptors were L-histidine, L-asparagine, L-aspartate, L-glutamate and L-proline, but L-glutamine was a very poor acceptor. The enzyme was very sensitive to inhibition by 6-diazo-5-oxo-L-norleucine (k2 = 4.0 X 10(5)/M per min) and O-diazo-acetyl-L-serine (k2 = 1.1 X 10(4)/M per min). Phenobarbital (k2 = 8.38/M per min) and L-serine borate (Ki = 34 mM) were poor inhibitors. The activity of the enzyme was not correlated with the logarithmic phase of growth of the parasites and steadily decreases with the age of the cultures.
克氏锥虫前鞭毛体表现出γ-谷氨酰转肽酶活性，其特性与哺乳动物的酶有显著差异。原生动物酶定位于胞质部分，以L-γ-谷氨酰-对硝基苯胺作为γ-谷氨酰供体时，其Km为1.6 mM，Vmax为17.4 nmol/min/mg蛋白质，最适pH范围为7.5至8.0。最佳氨基酸受体为L-组氨酸、L-天冬酰胺、L-天冬氨酸、L-谷氨酸和L-脯氨酸，但L-谷氨酰胺是非常差的受体。该酶对6-重氮-5-氧代-L-正亮氨酸（k2 = 4.0×10(5)/M每分钟）和O-重氮乙酰-L-丝氨酸（k2 = 1.1×10(4)/M每分钟）的抑制非常敏感。苯巴比妥（k2 = 8.38/M每分钟）和L-丝氨酸硼酸盐（Ki = 34 mM）是较差的抑制剂。该酶的活性与寄生虫生长的对数期无关，且随着培养物年龄的增长而稳步下降。
