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Journal of Bacteriology, July 2000, p. 3655-3660, Vol. 182, No. 13
Institut für Biochemie und
Lebensmittelchemie, Technische Universität Graz, A-8010 Graz,
Austria
Received 20 January 2000/Accepted 18 April 2000
Saccharomyces cerevisiae medium-chain acyl elongase
(ELO1) mutants have previously been isolated in screens for
fatty acid synthetase (FAS) mutants that fail to grow on myristic acid
(C14:0)-supplemented media. Here we report that wild-type cells
cultivated in myristoleic acid (C14:1
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Elo1p-Dependent Carboxy-Terminal Elongation of
C14:1
9 to C16:1
11 Fatty Acids in
Saccharomyces cerevisiae
9)-supplemented
media synthesized a novel unsaturated fatty acid that was identified as
C16:1
11 fatty acid by gas chromatography-mass
spectroscopy. Synthesis of C16:1
11 was dependent on a
functional ELO1 gene, indicating that Elo1p catalyzes
carboxy-terminal elongation of unsaturated fatty acids (
-elongation). In wild-type cells, the C16:1
11
elongation product accounted for approximately 12% of the total fatty
acids. This increased to 18% in cells that lacked a functional acyl
chain desaturase (ole1
mutants) and hence were fully
dependent on uptake and elongation of C14:1. The observation that
ole1
mutant cells grew almost like wild type on medium
supplemented with C14:1 indicated that uptake and elongation of
unsaturated fatty acids were efficient. Interestingly,
wild-type cells supplemented with either C14:1 or C16:1 fatty acids
displayed dramatic alterations in their phospholipid composition,
suggesting that the availability of acyl chains is a dominant
determinant of the phospholipid class composition of cellular
membranes. In particular, the relative content of the two major
phospholipid classes, phosphatidylethanolamine and phosphatidylcholine,
was strongly dependent on the chain length of the supplemented fatty
acid. Moreover, analysis of the acyl chain composition of individual
phospholipid classes in cells supplemented with C14:1 revealed that the
relative degree of acyl chain saturation characteristic for each
phospholipid class appeared to be conserved, despite the gross
alteration in the cellular acyl chain pool. Comparison of the
distribution of fatty acids that were taken up and elongated
(C16:1
11) to those that were endogenously synthesized by
fatty acid synthetase and then desaturated by Ole1p
(C16:1
9) in individual phospholipid classes finally
suggested the presence of two different pools of diacylglycerol
species. These results will be discussed in terms of biosynthesis of
different phospholipid classes via either the de novo or the Kennedy pathway.
*
Corresponding author. Mailing address: Institute of
Biochemistry, Technical University Graz, Petersgasse 12, A-8010 Graz, Austria. Phone: 43-316-873-6955. Fax: 43-316-873-6952. E-mail: f548roge{at}mbox.tu-graz.ac.at.
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