Camel lens zeta-crystallin kinetics and its inhibition by dicoumarol.
zeta-Crystallin a novel NADPH quinone oxidoreductase of the camel lens is capable of reducing a non quinone compound such as 2,6-dichlorophenolindophenol (DCIP) which is mediated by NADPH. A classical Michaelis-Menten kinetics were exhibited for both DCIP and NADPH with Km values of 15.3 microM and 7.0 microM respectively, at pH 7.8. The Vmax was 1.60 mumol./min.mg protein. The results of steady-state kinetic analysis indicated that the reaction proceeds through a Ping-Pong mechanism. Dicoumarol was found to be a competitive inhibitor of zeta-crystallin with respect to DCIP with a Ki value of 14.6 microM and showed uncompetitive inhibition with respect to NADPH with a Ki value of 36.2 microM.
Duhaiman
A S
AS
Department of Biochemistry, King Saud University, Riyadh, Saudi Arabia.
D015086:2,6-Dichloroindophenol / Q000378:metabolism; D000818:Animals; D002162:Camelus; D003459:Crystallins / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D001728:Dicumarol / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009249:NADP / Q000378:metabolism
D003459:Crystallins; D004791:Enzyme Inhibitors; D009249:NADP; D001728:Dicumarol; D015086:2,6-Dichloroindophenol