Dvoráková L, Krůsek J, Stastný F, Lisý V
Institute of Physiology, Academy of Sciences of the Czech Republic, Czech Republic.
Gen Physiol Biophys. 1996 Oct;15(5):403-13.
The initial rate kinetics of rat kidney gamma-glutamyl transpeptidase were measured using L-gamma-glutamyl-p-nitroanilide and glycyl-glycine as the donor and the acceptor substrate, respectively. Experimental data were fitted with the initial rate equation, and the obtained results indicated that: (1) Michaelis constants for transpeptidation (Kb), autotranspeptidation (Ka), and hydrolysis (Kh) are 8.56 mmol/l, 2.02 mmol/l and 0.005 mmol/l, respectively. (2) The maximum rate of transpeptidation (Vb) exceeds that of hydrolysis (Vh) and autotranspeptidation (Va) 160 times and 5 times, respectively. (3) A comparison of the ratios of maximal rate: Michaelis constant of individual reactions shows that hydrolysis is approximately 10 times more efficient than the remaining two reactions. (4) Under routine conditions used for gamma-glutamyl transpeptidase estimation, transpeptidation is the prevalent reaction.
分别使用L-γ-谷氨酰-对硝基苯胺和甘氨酰甘氨酸作为供体底物和受体底物，测定大鼠肾脏γ-谷氨酰转肽酶的初始速率动力学。实验数据用初始速率方程拟合，所得结果表明：（1）转肽作用（Kb）、自身转肽作用（Ka）和水解作用（Kh）的米氏常数分别为8.56 mmol/l、2.02 mmol/l和0.005 mmol/l。（2）转肽作用的最大速率（Vb）分别超过水解作用（Vh）和自身转肽作用（Va）160倍和5倍。（3）对各个反应的最大速率与米氏常数之比进行比较，结果表明水解作用的效率比其余两个反应高约10倍。（4）在用于γ-谷氨酰转肽酶测定的常规条件下，转肽作用是主要反应。
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