An Atypical Substrate–inhibitor–Rate Relationship for the Action of Antimycin A on the Succinate–Ferricyanide Reductase Activity of Beef Heart Electron Transfer Particles

The degree of inhibition of the succinate–ferricyanide reductase activity of beef heart electron transfer particles by antimycin A is negligible at low succinate concentrations (< 1 mM) but increases to about 40% at saturating concentrations of succinate. This behavior is explained on the basis of a random order mechanism for the primary dehydrogenase with alternative routes from the monosubstrate complexes, only one of which is sensitive to antimycin.