Inhibition of purified bovine liver glutathione reductase with some metal ions

Abstract

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 μM–10 mM concentrations, Al³⁺, Ba²⁺, Li⁺, Mn²⁺, and Mo⁶⁺, and Ca²⁺ at 5 μM–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.

Keywords::

• Glutathione reductase
• bovine liver
• inhibition
• kinetics
• metal ions

Acknowledgment

This work is part of a project (0701101011 and 02 G085) supported by the Hacettepe University Scientific Research Unit.

Declaration of interest: The authors report no conflicts of interest.