Document Detail

Evolutionarily conserved Delta(25(27))-olefin ergosterol biosynthesis pathway in the alga Chlamydomonas reinhardtii.
MedLine Citation:
PMID:  22591742     Owner:  NLM     Status:  MEDLINE    
Ergosterol is the predominant sterol of fungi and green algae. Although the biosynthetic pathway for sterol synthesis in fungi is well established and is known to use C24-methylation-C24 (28)-reduction (Δ(24(28))-olefin pathway) steps, little is known about the sterol pathway in green algae. Previous work has raised the possibility that these algae might use a novel pathway because the green alga Chlamydomonas reinhardtii was shown to possess a mevalonate-independent methylerythritol 4-phosphate not present in fungi. Here, we report that C. reinhardtii synthesizes the protosterol cycloartenol and converts it to ergosterol (C24β-methyl) and 7-dehydroporiferasterol (C24β-ethyl) through a highly conserved sterol C24- methylation-C25-reduction (Δ(25(27))-olefin) pathway that is distinct from the well-described acetate-mevalonate pathway to fungal lanosterol and its conversion to ergosterol by the Δ(24(28))-olefin pathway. We isolated and characterized 23 sterols by a combination of GC-MS and proton nuclear magnetic resonance spectroscopy analysis from a set of mutant, wild-type, and 25-thialanosterol-treated cells. The structure and stereochemistry of the final C24-alkyl sterol side chains possessed different combinations of 24β-methyl/ethyl groups and Δ(22(23))E and Δ(25(27))-double bond constructions. When incubated with [methyl-(2)H(3)]methionine, cells incorporated three (into ergosterol) or five (into 7-dehydroporiferasterol) deuterium atoms into the newly biosynthesized 24β-alkyl sterols, consistent only with a Δ(25(27))-olefin pathway. Thus, our findings demonstrate that two separate isoprenoid-24-alkyl sterol pathways evolved in fungi and green algae, both of which converge to yield a common membrane insert ergosterol.
Matthew B Miller; Brad A Haubrich; Qian Wang; William J Snell; W David Nes
Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2012-05-16
Journal Detail:
Title:  Journal of lipid research     Volume:  53     ISSN:  0022-2275     ISO Abbreviation:  J. Lipid Res.     Publication Date:  2012 Aug 
Date Detail:
Created Date:  2012-07-16     Completed Date:  2012-11-23     Revised Date:  2013-08-14    
Medline Journal Info:
Nlm Unique ID:  0376606     Medline TA:  J Lipid Res     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1636-45     Citation Subset:  IM    
Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409, USA.
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MeSH Terms
Alkenes / chemistry*
Chlamydomonas reinhardtii / metabolism*
Ergosterol / biosynthesis*,  chemistry*,  metabolism
Evolution, Molecular*
Methionine / metabolism
Grant Support
Reg. No./Substance:
0/Alkenes; 57-87-4/Ergosterol; 63-68-3/Methionine

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