Mitochondrial complex III (EC 1.10.2.2), also known as CoQ-cytochrome C reductase, is widely found in
mitochondria of animals, plants, microorganisms and cultured cells. It is a common component of the main
pathway and branch of the mitochondrial respiratory electron transport chain. Mitochondrial complex III is
responsible for transferring hydrogen from reduced CoQ to cytochrome C and then produce reduced
cytochrome C.
Unlike oxidized cytochrome C, reduced cytochrome C has a characteristic absorption at 550 nm, so the
rate of increase in light absorption at 550 nm can reflect mitochondrial complex III enzyme activity.
Reagents and Equipment Required but Not Provided:
Spectrophotometer/ Microplate reader, water bath, desk centrifuge, transferpettor, micro glass cuvette/ 96-
well flat-bottom plate (non-polystyrene material), mortar/ homogenizer, ice and distilled water.
