Anteiso fatty acids

Chemical Composition. Wool wax is a complex mixture of esters of water-soluble alcohols (168) and higher fatty acids (169) with a small proportion (ca 0.5%) of hydrocarbons (170). A substantial effort has been made to identify the various components, but results are compHcated by the fact that different workers use wool waxes from different sources and employ different analytical techniques. Nevertheless, significant progress has been made, and it is possible to give approximate percentages of the various components. The wool-wax acids (Table 9) are predominantiy alkanoic, a-hydroxy, and CO-hydroxy acids. Each group contains normal, iso, and anteiso series of various chain length, and nearly all the acids are saturated. 

Many substituted, ie, branched, fatty acids, particularly methacryUc, 2-ethylhexanoic, and ricinoleic acids, are commercially significant. Several substituted fatty acids exist naturally (Table 5). Fatty acids with a methyl group in the penultimate position are called iso acids, and those with a methyl group in the antepenultimate position are called anteiso acids (1) (see Carboxylic acids, branched-CHAIN acids). However, the term iso is often used in a broader sense to mean branched or mixtures of branched-chain industrial acids. 

Fig. 21.15. Partial gas chromatogram of extracted lipids. Peaks Ci4 0 to Ci8 o> saturated straight fatty chain acids (FA) with 14 to 18 carbon atoms C45br and Ci7 r, iso- and anteiso- branched-chain fatty acids Ci8 i FA, mono-unsatu-rated CigtoOH-FA, hydroxylated form derived by bacterial hydration of the original oleic acid. (Reprinted/redrawn from Nature, 432, 35-36, Copyright 2004, Nature Publishing Group, with permission.)...

Massart-Leen et al. (1981) analyzed bovine milk fat and goat milk fat for branched chain fatty acids. They did not find the same diversity of fatty acids in bovine as in goat milk fat and as previously reported. The authors suggested that the difference—the absence of branched chain acids other than iso and anteiso in bovine milk fat—could be caused by the relative inefficiency of the incorporations of methylmalonic acid into the biosynthetic pathway. 

Branched fatty acids of the anteiso series have a branch here and a 5-carbon "starter piece" derived from isoleucine... 

Their study agrees with the Myher et al. (130) estimation in the identification of TGs with odd-carbon-number fatty acids (CN = 15 and 17), either branched or linear. However, they have been able to differentiate between iso and anteiso isomers not only in the GLC analysis of fatty acids but also in TG estimation. Tridecanoic and nonadecanoic acids were identified by GLC but were not included in TG estimation due to their low amounts in whole milk fat content. 

T Kaneda. Iso- and anteiso-fatty acids in bacteria biosynthesis, function and taxonomic significance. Microbiol Rev 55 288-302, 1991. 

Branched-chain fatty acids (BrFAs) (iso- and anteiso) are believed to be primarily derived from sulfate-reducing bacteria (Perry et al., 1979 Cranwell, 1982 Canuel et al., 1995 table 9.5). However, it should be noted that BrFAs are not present in all sulfate-reducing bacteria or other heterotrophic bacteria (Kaneda, 1991 Kohring et al., 1994). The iso- and antesio- designation represents a branched fatty acid with the methyl group at the a>-l position and the methyl group at the a>-2 position, respectively. The odd number (C45, C17, branched and normal) are believed to be derived from phospholipids, components of bacterial cell membranes (Kaneda, 1991). Even-numbered iso-branched fatty acids (e.g., C12—Cig) are also found in algal sources (Schnitzer and Khan, 1972). 

Branched fatty acids iso- and anteiso fatty acids believed to be primarily derived from sulfate-reducing bacteria the iso- and antesio designation represents a branched fatty acid with the methyl group at the w-1 position and the methyl group at the co-2 position, respectively. 

Linear capsiacinoids with a C9/C12 chain are only trace constituents of capsicum oleoresin, which mainly contains branched capsaicinoids. The acyl moiety of these compounds is produced by the branched chain fatty acids pathway (Scheme 4.1) [30[. Depending on the nature of the amino acid that acts as the acyl starter precursor, different capsaicinoids are formed. Thus, capsaicinoids of the iso series such as CPS and homocapsaicin I are derived from valine and leucine via isobutyrylCoA and isovalerylCoA, respectively, while those from the anteiso series such as homocapsaicin II originate from isoleucine via 2-methylbutyrylCoA (Scheme 4.1) [31[. The polymethylene moiety of norcapsaicin has one less carbon than capsaicin. The... 

The basic fish oil (27) also included a generous amount of saturated fatty acids. As can be seen from Figure 5 and Table 1, the saturated fatty acids are dominated by the 16 0 (palmitic acid), usually accompanied by about half as much or less of 14 0 (myristic acid) and much less of 18 0 (stearic acid). Usually the saturated fatty acid totals are at least 20%, especially as the odd chain (15 0, 17 0) and methyl-branched (iso, anteiso, pristanic, phytanic) fatty acids (compare Figure 4) are sam-rated and will total around 2-3%. An unsaturated peak that is often observed is 17 ln-8, which is roughly equal to 17 0. The details of these peaks are discussed in other publications, but those researchers attempting modern open-tubular gas chromatography analyses should be aware of their presence and influence on peak identification and quantitation. As can be seen from Figure 6, there is an... 

The peaks for C14 monounsaturated fatty acids follow 14 0 and are usually a jumble of peaks for 14 1 isomers, mixed up with those for iso and anteiso 15 0 and the isoprenoid 4,8,12-trimethyltridecanoic acid, followed reasonably clearly by that for 15 0 (Table 2). Little interest exists in these details, and the only obvious next peak before 16 0 should be iso-16 0, and sometimes another isoprenoid acid, pristanic or 2,6,10,14-tetramethylpentadecanoic, is found just ahead of 16 0. 

This paper presents data on isolation and identification of the following types of geolipids from the Aleksinac oil shale, a Miocene lake sediment n-al-kanes, iso- and/or anteiso-alkanes, aliphatic iso-prenoid alkanes, polycyclic isoprenoid alkanes, aromatic hydrocarbons, saturated unbranched, aliphatic isoprenoid, hopanoic, and aromatic mono- and poly-carboxylic acids, fatty acid methyl esters, aliphatic y- and 6-lactones, cyclic y-lactones, aliphatic methyl- and isoprenoid ketones, and the triterpenoid ketone adiantone. Possible origin of the identified compound classes is discussed, particularly of those which had not been identified previously as geolipids. 

Recently, a unique anteiso methyl-branched saturated fatty acid of 21 carbons, 18-methyl eicosanoic acid or 18-MEA, was identified in the outermost portion of the epicuticle, which is part of the CMC [104,106-110], 18-MEA is the predominant fatty acid in the epicuticle. It makes up approximately 40% of the surface lipid layer of wool and human hair [106,107,109], In addition to 18-MEA, other fatty acids have been isolated in smaller amounts from the epicuticle including... 

These branched acids can be source-specific and they are rarely unsaturated. They are formed by the incorporation of branched amino acids into the biosynthetic pathway, yielding iso and anteiso acids, as noted in Section 5.1.3. Iso and anteiso saturated fatty acids are found in fungi, molluscs and phytoplankton, but they are generally in higher levels in bacteria and are often observed in the C13—C17 range (Harwood Russell 1984).The C15 isomers (Fig. 5.1) are usually particularly abundant in bacteria and the ratio (iso + anteiso)/normal derived from C15 components can be used as an indication of relative bacterial contributions (Parkes Taylor 1983). Similarly, the (08 isomers of /. >- 5 1 and iso-17 1 are bacterial markers (Perry et al. 1979), and iso-17 1(07 is characteristically a major fatty acid in the sulphate-reducing bacteria Desulfovibrio desulfuricans (Taylor Parkes 1983). 

Abbreviations a-BFAs anteiso-branched fatty acids AGP acyl carrier protein BHLH active soluble domain of SREBP CNS central nervous system DSD delta 5 desaturase D6D delta 6 desaturase ER endoplasmic reticulum Hik histidine kinase HUFA highly unsaturated fatty acid LXR liver X receptor MUFA monounsaturated fatty add NF-Y nuclear factor Y PLs phospholipids PP peroxisome proliferator PPAR PP-activated receptor PPRE PP response element PUFA polyunsaturated fatty acid PUFA-BP PUFA binding protein PUFA-RE PUFA response element RXR retinoid X receptor SCAP SREBP cleavage-activating protein SCD steraroyl CoA desaturase SFA saturated fatty acid SRE sterol response... 

Other bacteria use different systems to regulate fluidity. For example, gram-positive bacteria alter the ratio of iso- to anteiso-branched-chain fatty acids in response to temperature [20]. However, the biochemical mechanisms that govern this universal response to environmental temperature are largely unknown in most bacterial species. 

The synthesis of an iso-anteiso pair of 5,9-21 2 fatty acids, namely the 19-methyleicosa-5,9-dienoic acid (16) and 18-methyleicosa-5,9-dienoic acid (17), prominent constituents of the phospholipids of the sponge... 

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