Mitochondrial complex II, also known as succinate-coenzyme Q reductase, is widely found in the mitochondria of animals, plants, microorganisms and cultured cells. It catalyzes the oxidation of succinic acid in the TCA cycle to fumaric acid, which converts the ubiquinone to a reduced form through the basic unit structures of the complex such as iron-sulfur proteins. Coenzyme Q, the catalytic product of mitochondrial complex II, can further reduce 2, 6-dichloroindoxol, which has a characteristic absorption peak at 600 nm. Therefore, the activity of mitochondrial complex II can be quantified by measure the change OD value at 600 nm.
