The terms succinate dehydrogenase and fumarate reductase may be used interchangeably in certain systems. However, a number of species have distinct complexes, with the fumarate reductase active under anaerobic conditions. This model represents the fumarate reductase flavoprotein subunit from several such species in which a distinct succinate dehydrogenase is also found. Not all bona fide fumarate reductases will be found by this model.
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