Succinate dehydrogenase enzyme. Molecular model of the succinate dehydrogenase (complex II) enzyme from an Escherichia coli bacterium. Succinate dehydrogenase is an enzyme that binds to the inner mitochondrial membrane in both mammalian and bacterial cells. It is part of both the citric acid cycle and the electron transport chain, metabolic processes that generate energy. In the citric acid cycle this enzyme plays a role in the reduction of ubiquinone (coenzyme Q10).