Metabolism of sterols by anaerobic Saccharomyces cerevisiae.

Anaerobically grown Saccharomyces cerevisiae retained the ability to transfer a C1-group to the C-24 position of a delta 24(25)-sterol and to reduce the delta 25(28)-bond of a 24-methylenesterol. Both desmosterol and 24-methylenecholesterol yielded 24 beta-methylcholesterol. However, when the substituent at C-24 was enlarged to a 24-ethylidene group (fucosterol), reduction of the delta 24(28)-bond did not occur. In no cases was a delta 7- or a delta 22-bond introduced. Because the delta 24(28)-bond was reduced in the absence of the delta 22-bond, the delta 22-bond is not an obligatory requirement for reduction.