The document summarizes several key enzymatic reactions in the citric acid cycle, including the formation of citric acid by citrate synthase, the isomerization of cis-aconitate to isocitrate catalyzed by aconitase, the oxidation of isocitrate to alpha-ketoglutarate catalyzed by isocitrate dehydrogenase, the hydrolysis of succinyl-CoA and formation of GTP catalyzed by succinyl-CoA synthase, the oxidation of succinate to fumarate by succinate dehydrogenase, the hydration of fumarate to malate catalyzed by fumarase, and the oxidation of malate to oxaloacetate catalyzed by