Phytosterol biosynthesis pathway in Mortierella alpina

W. David Nes, Shawn D. Nichols

Research output: Contribution to journalArticle

12 Scopus citations

Abstract

The Zygomycetes fungus Mortierella alpina was cultured to growth arrest to assess the phytosterol biosynthesis pathway in a less-advanced fungus. The mycelium was found to produce 13 sterols, but no ergosterol. The sterol fractions were purified to homogeneity by HPLC and their identifies determined by a combination of GC-MS and 1H NMR spectroscopy. The principal sterol of the mycelium was cholesta-5, 24-dienol (desmosterol) (83%), with lesser amounts of 24β-methyl-cholesta-5,25(27)-dienol (codisterol) (2%), 24-methyldesmosterol (6%), 24(28)-methylene cholesterol (3%) and lanosterol (3%) and several other minor compounds (3%). The total sterol accounted for approximately 0.07% of the mycelial dry wt. Mycelium fed methionine-methyl-2H3 for 6 days, generated 3 2H-24-methyl(ene) sterols, [C28-2H2]24(28)-methylenecholesterol, [C28-2H3]24-methylcholesta-5,24-dienol and [C28-2H3]24β-methyl-cholesta-5,25(27)-dienol. The formation of the 24-methyl sterols seems to be catalyzed by the direct methylation of a common Δ24-acceptor sterol thereby bypassing the intermediacy of an isomerization step for rearrangement of the Δ24(28)-bond to Δ25(25)-position as operates in Ascomycetes fungi and all plants.

Original languageEnglish
Pages (from-to)1716-1721
Number of pages6
JournalPhytochemistry
Volume67
Issue number16
DOIs
StatePublished - Aug 2006

Keywords

  • Cholesterol
  • Ergosterol biosynthesis
  • Fungal evolution
  • Isotope labeling
  • Mortierella alpina
  • Sterol methyltransferase

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