Inhibition of purified bovine liver glutathione reductase with some metal ions.
Glutathione reductase (GR; E.C. 1.6.4.2) is a flavoprotein that catalyzes the NADPH-dependent reduction of oxidized glutathione (GSSG). In this study we tested the effects of Al3+, Ba2+, Ca2+, Li+, Mn2+, Mo6+, Cd2+, Ni2+, and Zn2+ on purified bovine liver GR. In a range of 10 microM-10 mM concentrations, Al3+, Ba2+, Li+, Mn2+, and Mo6+, and Ca2+ at 5 microM-1.25 mM, had no effect on bovine liver GR. Cadmium (Cd2+), nickel (Ni2+), and zinc (Zn2+) showed inhibitory effects on this enzyme. The obtained IC50 values of Cd2+, Ni2+, and Zn2+ were 0.08, 0.8, and 1 mM, respectively. Cd2+ inhibition was non-competitive with respect to both GSSG (Ki(GSSG) 0.221 +/- 0.02 mM) and NADPH (Ki(NADPH) 0.113 +/- 0.008 mM). Ni2+ inhibition was non-competitive with respect to GSSG (Ki(GSSG) 0.313 +/- 0.01 mM) and uncompetitive with respect to NADPH (Ki(NADPH) 0.932 +/- 0.03 mM). The effect of Zn2+ on GR activity was consistent with a non-competitive inhibition pattern when the varied substrates were GSSG (Ki(GSSG) 0.320 +/- 0.018 mM) and NADPH (Ki(NADPH) 0.761 +/- 0.04 mM), respectively.
Tandogan
Berivan
B
Department of Biochemistry, Faculty of Medicine, Hacettepe University, Ankara, Turkey.
Ulusu
N Nuray
NN
D000818:Animals; D002417:Cattle; D005980:Glutathione Reductase / Q000037:antagonists & inhibitors*; D007700:Kinetics; D008099:Liver / Q000187:drug effects* / Q000201:enzymology; D008670:Metals / Q000494:pharmacology*
D008670:Metals; D005980:Glutathione Reductase