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Analysis of kinetic properties of gamma-glutamyl transpeptidase from rat kidney.

General physiology and biophysics (1996-10-01)
L Dvoráková, J Krůsek, F Stastný, V Lisý
RÉSUMÉ

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.

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Sigma-Aldrich
L-Glutamic acid γ-(p-nitroanilide) hydrochloride, γ-glutamyl transpeptidase substrate
Sigma-Aldrich
L-Glutamic acid γ-(4-nitroanilide), γ-glutamyl transpeptidase substrate