Sterol Biosynthesis in Fungi

Abstract

The observation that lanosterol but not zymosterol is converted into ergosterol by yeast preparations (Schwenk & Alexander, 1958) indicates that trans- methylation occurs at an early stage in the biosynthetic pathway. Some wood-rotting fungi contain acidic triterpenes (e.g. eburicoic acid and the polyporenic acids; see Fieser & Fieser, 1959) that have a methylene group at C-24, showing that transmethylation occurs, at least in these organisms, at the lanosterol level. The possibility that trans- methylation also occurs immediately after squalene cyclization in ergosterol biosynthesis is supported by recent reports of the conversion of synthetic labelled 24-methylenelanosterol into ergosterol by yeast (Akhtar, Parvez & Hunt, 1966b; Barton, Harrison & Moss, 1966).