Fumarate reductase yeast

All aerobic organisms, including yeast, appear to have a membrane-bound succinate dehydrogenase containing iron and covalently bound flavin 15, 16, 25). In contrast, the enzyme in anaerobic organisms is found in the cytoplasm and appears to be more effective as a fumarate reductase, a modification which is in accord with the physiological requirements of the organism. In facultative anaerobes such as E. coli and... 

Tisdale et al. (222) have shown that several isozymes of fumarate reductase occur in brewer s yeast, ranging in molecular weight from 34,000 to 112,000. The predominant species had a molecular weight of 62,000-... 

In the reductive pathway, the Krebs cycle enzymes are assumed to operate as far as a-oxoglutarate, thus forming a linear pathway. A second linear pathway, from oxaloacetate to malate to fumarate to succinate, is suggested to account for the formation of succinic acid [46]. In support of this new pathway are the observations that (/) yeast contains cytoplasmic malate dehydrogenases capable of converting oxaloacetate to malate, (//) several fumarate reductases (FAD-dependent) have been found in the yeast cytoplasm which have high affinity for fumarate and are unable to oxidize succinate [52] and (Hi) succinate is a significant product of fermentation, i.e. an end product . 

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