Fatty acid in eukaryotes

The addition of double bonds to fatty acids in eukaryotes does not occur until the fatty acyl chain has reached its full length (usually 16 to 18 carbons). Dehydrogenation of stearoyl-CoA occurs in the middle of the chain despite the absence of any useful functional group on the chain to facilitate activation ... 

Erwin, Comparative biochemistry of fatty acids in eukaryotic microorganisms "Lipids and Biomembranes of Eukaryotic Microorganisms", J.A. Erwin, ed, Academic Press, New York (1973). 

Lipoxygenases, of which the enzyme from soy beans has been studied the most, also catalyze oxidation of polyunsaturated fatty acids in lipids as indicated in Eq. 21-17. Formation of the hydroperoxide product is accompanied by a shift of the double bond and conversion from cis to trans configuration. Soybean lipoxygenase is a member of a family of related lipoxygenases that are found in all eukaryotes. All... 

Schulz, H., Oxidation of fatty acids. In D. E. Vance, and J. E. Vance (eds.), Biochemistry of Lipids, Lipoproteins and Membranes. Amsterdam Elsevier Science Publishers, 1991. Provides an advanced and current summary of fatty acid oxidation in prokaryotes and eukaryotes. 

Synthesis of most phospholipids starts from glycerol-3-phosphate, which is formed in one step from the central metabolic pathways, and acyl-CoA, which arises in one step from activation of a fatty acid. In two acylation steps the key compound phosphatidic acid is formed. This can be converted to many other lipid compounds as well as CDP-diacylglycerol, which is a key branchpoint intermediate that can be converted to other lipids. Distinct routes to phosphatidylethanolamine and phosphatidylcholine are found in prokaryotes and eukaryotes. The pathway found in eukaryotes starts with transport across the plasma membrane of ethanolamine and/or choline. The modified derivatives of these compounds are directly condensed with diacylglycerol to form the corresponding membrane lipids. Modification of the head-groups or tail-groups on preformed lipids is a common reaction. For example, the ethanolamine of the head-group in phosphatidylethanolamine can be replaced in one step by serine or modified in 3 steps to choline. 

Compartmentation. The metabolic patterns of eukaryotic cells are markedly affected by the presence of compartments (Figure 30 3). The fates of certain molecules depend on whether they are in the cytosol or in mitochondria, and so their flow across the inner mitochondrial membrane is often regulated. For example, fatty acids are transported into mitochondria for degradation only when energy is required, whereas fatty acids in the cytosol are esterified or exported. 

Jiang, Y., Vasconcelles, M.J., Wretzel, S., Light, A., Gilooly, L., McDaid, K., Oh, C.S., Martin, C.E. and Goldberg, M.A. Mga2p processing by hypoxia and unsaturated fatty acids in Saccharomyces cerevisiae impact on LORE-dependent gene expression. Eukaryot Cell, 1 (2002) 481-490. 

Uttaro, A.D. Biosynthesis of polyunsaturated fatty acids in lower eukaryotes. lUBMB Life, 58 (2006) 563-571. 

Introduction Primary Fatty Acids Fatty Acids of Plant Vegetative Parts Biosynthesis Fatty Acid Biosynthesis The Two-Pathway Model of Lipid Biosynthesis The Second 3-Ketoacyl ACP Synthase Isozyme Biosynthesis of Unsaturated Fatty Acids The Prokaryotic Pathway The Eukaryotic Pathway Biosynthesis of Triacylglycerides Degradation of Fatty Acids Unusual Fatty Acids in Plants Fatty Acids from Unusual Starter Units Fatty Acids with Unusual Patterns of Unsaturation Hydroxy Fatty Acids Epoxy Fatty Acids... 

The CPTi and CPTo of the pea chloroplast inner envelope are ideally placed to facilitate the export/import of fatty acids in the eukaryotic pathv/ay of fatty acid desaturation and provide an additional, alternative pathway to the one currently proposed in the literature [1]. 

The lipid composition of the HZ3 mutant demonstrated a three fold increase in the proportion of TAGs and a corresponding decrease in that of PC in comparison to the wild type (Table I). Moreover, the proportion of EPA of the mutant decreased from 41.1% (of total fatty acids) in the wild type to 26.5%. These alterations were most noticeable in MGDG where the proportion of EPA was reduced from 56 to 45.5%. The molecular species composition of MGDG demonstrated a decrease in the proportion of the major eukaryotic species 20 5/20 5 which was accompanied by increases in the prokaryotic species 18 2/16 0, 20 4/16 0 and 20 5/16 0 (Table I). DGDG which is entirely prokaryotic, was not significantly affected. We have interpreted this as an indication that the mutation affected the eukaryotic pathway. 

Autoradiography of the labelled fatty acids in position sn-2 of MGDG (not shown) indicated only traces of label in the area covered by 16 0 (prokaryotic galactolipid) in EC while this area was well labelled in NY 18 2 and 18 3 were well labelled in both cultivars (eukaryotic pathway). 

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