Abstract
The electron spin resonance method has been used to study the effect of pH on the apparent oxidation-reduction potential of heart muscle succinic dehydrogenase over the pH range 6.5 to 8.5. This range lies beyond pKaz of the substrates, succinate and fumarate, but contains the range of pH where succinic dehydrogenase shows the highest ac- tivity in assay systems. The data suggest that dFo/dpH is 0 f 3 mv x pH-l. We discuss this finding in connection with the mechanism of action of succinic dehydrogenase under conditions of exchange in the absence of supplementary oxidation-reduction constituents.