ANALYSIS OF KINETIC-PROPERTIES OF GAMMA-GLUTAMYL-TRANSPEPTIDASE FROM RAT-KIDNEY

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 d ata were fitted with the initial rate equation, and the obtained resul ts indicated that: (1) Michaelis constants for transpeptidation (K-b), autotranspeptidation (K-a) and hydrolysis (K-h) are 8.56 mmol/l, 2.02 mmol/l and 0.005 mmol/l, respectively. (2) The maximum rate of transp eptidation (V-b) exceeds that of hydrolysis (V-h) and autotranspeptida tion (V-a) 160 times and 5 times, respectively. (3) A comparison of th e ratios of maximal rate: Michaelis constant of individual reactions s hows 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.