Inhibitory kinetic studies on rat hepatic and renal succinate dehydrogenase with guanidine

Guanidine-induced alterations in substrate dependent kinetics of hepatic and renal succinate dehydrogenase (SDH) have been investigated under in vitro conditions. Guanidine hydrochloride (GuHCl) induced a mixed type of inhibition by decreasing the maximal velocity (Vmax) and increasing the Michaelis-Menten constant (Km). The competitive (Ki) and non-competitive (Ki) inhibitory constants were calculated. The values showed that the inhibitory influence of GuHCl is more due to decreased enzyme substrate affinity rather than reduction in the active site density of the enzyme as revealed by low Ki values.