an enzyme of the oxidoreductase class that is prevalent in plant and animal cells, where it is localized in the inner membrane of mitochondria. Succinate dehydrogenase is one of the important enzymes involved in energy metabolism. In the tricarboxylic acid cycle, it catalyzes the reversible oxidation of succinic acid (succinate) to fumaric acid. The oxidation of one mole of succinic acid results in the synthesis of two moles of adenosine triphosphate (ATP). The electrons are transmitted from succinate dehydrogenase to the respiratory chain through coenzyme Q.

Succinate dehydrogenase, isolated in 1954 by the American scientist T. Singer, is structurally a flavoprotein; the protein constituent is covalently bound to the coenzyme flavin adenine dinucleotide (FAD). The enzyme contains eight atoms of nonheme iron as well as labile sulfur atoms. Sulfhydryl groups are believed to constitute part of the active center of succinate dehydrogenase.