A ‘branched’ mechanism of the reverse reaction of yeast glutathione reductase An estimation of the enzyme standard potential values from the steady-state kinetics data

The reduced glutathione-linked NADP + reduction, catalyzed by yeast glutathione reductase, follows a ‘sequential’ or ‘ping-pong’ mechanism at high or low NADP + concentrations, respectively. The pattern of the NADPH and NADP + cross-inhibition reflects not only the competition for the binding site, but the shift of the reaction equilibrium as well. A ‘branched’ scheme of the glutathione reductase reaction is presented. The enzyme standard potential (−255 mV, pH 7.0) was estimated from the ratio of the NADPH and NADP + rate constants corresponding to the ping-pong mechanism.