Succinate, fumarase inhibition

Succinyl CoA is cleaved by succinate thiokinase (also called succinyl CoA synthetase), producing succinate and ATP (or GTP). This is an example of substrate-level phosphory lation. Succinate is oxidized to fumarate by succinate dehydrogenase, producing FADH2. The enzyme is inhibited by oxaloacetate. Fumarate is hydrated to malate by fumarase (fumarate hydratase), and malate is oxidized to oxaloacetate by malate dehy drogenase, producing NADH. 

As an application of equation 7.6-5, consider the effect of pH on the inhibition constants of fumarase, which have been determined for succinate, D-tartrate, L-tartrate, and meso-tartrate inhibitors (Wigler and Alberty, 1960). The kinetics of the conversion of fumarate to L-malate and the inhibition by these competitive inhibitors indicate that there are two acid groups in the catalytic site that affect the binding ... 

The enzyme fumarase catalyzes the hydration of fumarate to malate. This enzyme is known to be reversibly inhibited by succinate. Reaction velocities were determined in triplicate at different substrate concentrations, in... 

The Oxaloacetic System (Szent-Gyoi i, 1937).— The wide distribution of the three enzymes, succinic and malic dehydrogenase, and fumarase, si ests that they and their respective substrates participate in many tissue respirations. Addition of malonic acid, which inhibits succinic acid oxidation, leads to an almost complete... 

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