Examination of the sterols of Gibberella fujikuroi has established that lanosterol (1), 24-methylene-24,25-dihydrolanosterol (2), 24-methyllanosterol (3, a new fungal sterol characterized herein by TLC, GLC, HPLC, MS and 1H-NMR techniques), obtusifoliol (4), 24β-methylcholesterol (5), 24β-methylcholesta-5,22-dienol (6, brassicasterol) and 24β-methylcholesta-5,7,22-trienol (7, ergosterol) are natural mycelial components, some of which are intermediates, while others are end-products playing bulk and regulating roles in fungal growth (Nes, W.D. and Heupel, R.C., Arch. Biochem. Biophys. 244 (1986) 211-217). Through feeding studies with 2-tritio-Δ23- and Δ24-24-methyllanosterol, 24-tritiolanosterol and [methyl-2H3]methionine, we now demonstrate that two alternative biosynthetic routes operate in the formation of 24β-methylsterol end-products. Route 1, 1 → 2 → 3 → 5; and route 2, 1 → 2 → 4 → 6 → 7. Route 2 involves the intermediacy of a Δ24(28)-sterol; which is reduced directly to produce the 24β-methyl group. Route 1 also passes through a Δ24(28)-sterol; however, prior to reduction the Δ24(28)-sterol is isomerized to a Δ24(28)-sterol. This is the first report that demonstrates that sterol biosynthesis in the more advanced fungi may involve separate pathways which do not crossover and converge into the track leading to ergosterol.
|Number of pages||7|
|Journal||Biochimica et Biophysica Acta (BBA)/Lipids and Lipid Metabolism|
|State||Published - Jan 16 1990|
- (G. fujikuroi)
- 24β-Methylsterol end-product
- Sterol biosynthesis
- Sterol intermediate