Oxidative decarboxylation reactions are oxidation reactions in which a carboxylate group is removed, forming carbon dioxide. They often occur in biological systems: there are many examples in the citric acid cycle. Oxidative decarboxylation reactions are oxidation reactions in which a carboxylate group is removed, forming carbon dioxide. They often occur in biological systems: there are many examples in the citric acid cycle. In the citric acid cycle pyruvate dehydrogenase, isocitrate dehydrogenase, and α-ketoglutarate dehydrogenase catalyze oxidative decarboxylation reactions. Each reaction reduces NAD+ to NADH and generates CO2. The transformation of glyoxylate to formic acid is also an oxidative decarboxylation.