A8(Q'22-Ergo~tadiene-3~-ol, an ergosterol precursor accumulated in wild-type and mutants of yeast

Whereas wild-type strains of Saccharomyces cerevisiae can synthesize up to 7% dry weight of ergosterol, a polyene- resistant mutant has been obtained which produces no er- gosterol. Instead, a C-28 methyl sterol is produced, and it has been identified as A8(9)~22-ergostadiene-3@-01. This sterol is converted to ergosterol by wild-type yeasts and is observed transiently in cells during aerobic adaption of anaerobically grown wild-type yeasts. The new sterol is proposed as an inter- mediate in ergosterol biosynthesis.