The effect of 2,4,6-trinitrobenzenesulfonate on mercuric reductase, glutathione reductase and lipoamide dehydrogenase

Abstract

Among the three closely related enzymes, lipoamide dehydrogenase, mercuric reductase, and glutathione reductase only the latter is inhibited by 2,4,6-trinitrobenzenesulfonate (TNBS). On the other hand, all three enzymes exhibit high rates of TNBS-dependent NADPH oxidation. In the case of glutathione reductase and mercuric reductase this TNBS-dependent activity displays substrate inhibition by excess of NADPH and is strongly stimulated by NADP +. The stimulation is especially pronounced with mercuric reductase, 25-fold under some conditions. Neither substrate inhibition nor stimulation by NAD + is observed with lipoamide dehydrogenase.