Occurrence of long-chain fatty acids and glycolipids in the cell-envelope fractions of baker's yeast

Abstract

1. The total yield of fatty acids from the whole envelopes was markedly higher than that obtained from the ordinary cell walls. In both samples the major fatty acids were C(16) and C(18) acids. 2. The whole envelopes contained C(18) acids and long-chain (C(19)-C(26)) fatty acids, in a higher proportion than did the ordinary cell walls. Fifteen fatty acids with more than 18 carbon atoms were identified, among which 2-hydroxy-C(26:0) and C(26:0) acids predominated. 3. A complex sphingolipid containing inositol, phosphorus and mannose was isolated from the whole cell envelopes. The main fatty acids of this lipid were 2-hydroxy-C(26:0) and C(26:0) acids. It was concluded that this sphingolipid is present both in the ordinary cell wall and in the plasma membrane of baker's yeast. 4. The neutral lipids amounted to over 50% and the glycerophosphatides to about 30% of the total fatty acid content of the whole envelope. The major fatty acids in these lipids were C(16:1), C(18:1) and C(16:0) acids. The proportion of fatty acids with more than 18 carbon atoms was lowest in the neutral lipids, whereas the neutral glycolipids contained the highest percentage of these fatty acids. Acidic glycolipids amounted to 14% of the total fatty acid content of the whole envelope. The presence of a cerebroside sulphate in this lipid fraction was demonstrated, whereas the high content of 2-hydroxy-C(26:0) acid found is caused by the complex inositol- and mannose-containing sphingolipid.

Fah1p, a Saccharomyces cerevisiae Cytochromeb 5 Fusion Protein, and ItsArabidopsis thaliana Homolog That Lacks the Cytochromeb 5 Domain Both Function in the α-Hydroxylation of Sphingolipid-associated Very Long Chain Fatty Acids

“…The low amount of ␣-HO 26:0 in the wild type alkali-labile fraction in trace e (ϳ0.1%) demonstrates, first, that virtually all sphingolipids are retained in the cell pellet by this method and, second, that there is a pool of 26:0 fatty acid that is not sphingolipid-bound. This is consistent with earlier reports that some 26:0 species are found in triglycerides (6). The absence of ␣-HO 26:0 in this pool also demonstrates the specificity of the hydroxylating enzyme for sphingolipid acyl groups.…”

A Yeast Acetyl Coenzyme A Carboxylase Mutant Links Very-Long-Chain Fatty Acid Synthesis to the Structure and Function of the Nuclear Membrane-Pore Complex

“…Such verylong-chain fatty acids are found in the ceramide moiety of sphingolipids, which are essential (49,65,85). Although the majority of sphingolipids localize to the yeast plasma membrane (32,59,63), some are also present in the nuclear membrane (3). The functional significance of the very long chain length of fatty acids of sphingolipids is underlined by the observation that strains which survive without sphingolipids produce novel C 26 fatty acid-containing glycerophospholipids, which structurally mimic sphingolipids (50).…”

Two Mammalian Longevity Assurance Gene (LAG1) Family Members, trh1 and trh4, Regulate Dihydroceramide Synthesis Using Different Fatty Acyl-CoA Donors

“…The current study extends the number of genes that regulate dihydroceramide synthesis in mammalian cells, and increases the likelihood that other mammalian Lag1p family members (16,17) also regulate (dihydro)ceramide synthesis with a high degree of fatty acid specificity. Interestingly, Saccharomyces cerevisiae SLs contain mainly one kind of N-linked fatty acid (namely C26) (32,33), and only two Lag1p family members (Lag1p/Lac1p) have been found to date in yeast. A much wider fatty acid distribution is found in SLs in mammalian cells where at least six Lag1p-motif-containing-proteins exist (16).…”