Phytanyl group

Ether-linked lipids constitute up to 35% of the total phospholipid in molluscs. Although they are usually regarded as animal constituents, small amounts of ether-linked lipids have been identified in plants. The major phospholipids of archaebacterial membranes are ether-linked derivatives of the polyprenyl phytanyl group and of the dimeric biphytanyl group (Chapter... 

Chain elongation during polymerization of prenyl units can be terminated in one of a number of ways. The pyrophosphate group may be hydrolyzed to a monophosphate or to a free alcohol. Alternatively, two polyprenyl compounds may join "head to head" to form a symmetric dimer. The C30 terpene squalene, the precursor to cholesterol, arises in this way from two molecules of famesyl diphosphate as does phy-toene, precursor of the Qo carotenoids, from E,E,E geranylgeranyl diphosphate. The phytanyl groups of archaebacterial lipids (p. 385) arise rather directly from geranylgeranyl diphosphate by transfer of the poly-... 

When cells of H. cutirubrum were grown in the presence of [ C]acetate, over 98% of the label was incorporated into the isopranyl (phytanyl) groups of the polar lipids, and less than 0.5% was found in long-chain fatty acids [86]. Cell-free studies subsequently demonstrated the presence of a fatty acid synthetase (FAS) which is largely ( 80%) inhibited by 4M NaCl or KC1[87]. However, sufficient FAS activity remains for the formation of saturated fatty acids (14 0, 16 0, 18 0) recently found to be esterified to proteins of the red membrane but not to bacteriorhodopsin in the purple membrane of extreme halophiles nor to the polar lipids (Pugh and Kates, unpublished data). 

A phytanyl chain contains 16 carbon atoms in the main chaim and 4 branched methyl groups. 

Other bacterial coats. Archaebacteria not only have unusual plasma membranes that contain phytanyl and diphytanyl groups (Section A,3)608 but also have special surface layers (S-Iayers) that may consist of many copies of a single protein that is anchored in the cell membrane.609 The surface protein of the hypothermic Staphylothermus marius consists of a complex structure formed from a tetramer of 92-kDa rods with an equal number of 85-kDa "arms."610 611 S-layers are often formed not only by archaebacteria but also by eubacteria of several types and with quite varied structures.612 14 While many bacteria carry adhesins on pili, in others these adhesive proteins are also components of surface layers.615 Additional sheaths, capsules, or slime layers, often composed of dextrans (Chapter 4) and other carbohydrates, surround some bacteria. 

Ferrante et al. [25,69] have shown that the lipids of Methanothrix (now Methanosaeta) concilii are derived from both archaeol and hydroxyarchaeol which has a hydroxyl group at C-3 of the phytanyl chain on the 5 -3-position (structure ID, Fig. 1) lipid cores. The major components are a Man/7-Gal-/J-archaeol (DGA-8, 24, Fig. 6), a Galp-Gal/7-hydroxyarchaeol (DGAqh-9, 25, Fig. 6), and archaeol-P-inositol (14, Fig. 6). Some minor components have now been identified [70] as archaeol-P-ethanolamine (15,... 

These archael membrane lipids consist of monopolar ether head groups and saturated, branched phytanyl chains which are... 

The diacylglycerol backbone in eubacteria and eukaryotes is sn-3-glycerol esterified at positions 1 and 2 with long-chain fatty acids (Fig. 2). In archaebacteria (Fig. 3), the opposite isomer sn-1-glycerol forms the lipid backbone and the hydrophobic domain is composed of phytanyl (saturated isoprenyl) groups in ether linkage at positions 2 and 3 (an archaeol)... 

Archaea are a group of organisms, previously classified as bacteria, from which eubacte-ria and other life may have evolved. A melavonic acid (six carbon)-building block is used for synthesis instead of acetic acid. The generated phytanyl chains are attached to glycerol moieties of complex lipids by ether linkages. Thus, these lipids are unlike anything found in eubacteria or eukaryotes today. 

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