Abstract
1. Bromopyruvate has been found to be a potent irreversible inhibitor of succinate dehydrogenase (succinate:(acceptor) oxidoreducatase, EC 1.3.99.1). While the kinetics of inactivation show a saturation effect, they do not fit the simple model for an active-site-directed irreversible inhibitor. Instead, a concentration dependent plateau is observed. A similar phenomenon occurs when N-ethylmaleimide is the alkylating agent. Reversible inhibitors and substrates protect succinate dehydrogenase from activation by bromopyruvate and N-ethylmaleimide. Both reagents have similar relative reactivities toward the enzyme and 2-nitro-5-thiolbenzoic acid dianion.
2. The absorption and dithionite bleaching spectra are not greatly affected by the reaction of enzyme with bromopyruvate, but the ability of succinate to bleach is lost. A decrease in hydrogen exchange capacity parallels the decrease in assay activity.