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.
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.