The enzyme, which is found in anaerobic and facultative organisms such as bacteria, parasitic helminthes, and lower marine organisms, utilizes low potential quinols, such as menaquinol and rhodoquinol, to reduce fumarate as the final step of an anaerobic respiratory chain. The enzyme is known as complex II of the electron transfer chain, similarly to EC
1.3.5.1, succinate dehydrogenase (quinone), to which it is closely related.
