Thiamine-induced alteration in sterol composition of Saccharomyces carlsbergensis 4228.

The cells of Saccharomyces carlsbergensis 4228 grown with added thiamine in a vitamin B-6-free medium did not contain ergosterol and zymosterol (the predominant sterols in cells grown without thiamine). Instead, significant amounts of squalene, lanosterol and unidentified sterols accumulated in the thiamine-grown cells. Of the unidentified sterols, the most predominant was delta5,7-ergostadien-3beta-ol at 26.0% of the total sterol. The accumulation of this sterol in the place or ergosterol (delta5,7,22-ergostatrien-3beta-ol) indicates that the desaturation at C-22 of sterol structure is completely blocked in the thiamine-grown cells. On the basis of chromatographic behaviours, the structures of other unidentified sterols were assumed to be 4alpha-methyl-delta8,24(25)-cholestadien-3beta-ol, 4alpha-methyl-delta 8,24(28)-ergostadien-3beta-ol, delta8,24(28)-ergostadien-3beta-ol and delta5,7,24(28)-ergostatrien-3beta-ol. The accumulation of 4alpha-methyl sterols, in addition to that of a large amount of lanosterol (48.4% of total sterol), suggests that the demethylation processes from lanosterol to zymosterol was partially depressed in the thiamine-grown cells.