Fatty acid cyclopropane containing

Bacteria usually lack polyunsaturated fatty acids but often contain branched fatty acids, cyclopropane-containing acids, hydroxy fatty acids, and unesterified fatty acids. Mycobacteria, including the human pathogen Mycobacterium tuberculosis, contain mycolic acids. In these compounds the complex grouping R contains a variety of functional groups including -OH, -OCH3,... 

In addition to unsaturated fatty acids, several other modified fatty acids are found in nature. Microorganisms, for example, often contain branched-chain fatty acids, such as tuberculostearic acid (Figure 8.2). When these fatty acids are incorporated in membranes, the methyl group constitutes a local structural perturbation in a manner similar to the double bonds in unsaturated fatty acids (see Chapter 9). Some bacteria also synthesize fatty acids containing cyclic structures such as cyclopropane, cyclopropene, and even cyclopentane rings. 

C=0, -COOH, cyclopropane rings, methyl branches, and C=C bonds. Each species of Mycobacterium contains about two dozen different mycolic acids910 as well as other complex C30-C56 fatty acids (see Eq. 21-5).11... 

Familial adenomatous polyposis 574 Faraday, numerical value of 283 Farnesyl group 402, 559 Fat(s). See also Triacylglycerol (triglyceride) composition of 380 hydrolysis of 507 Fatty acid(s) 380-382 activation of 512 acyl CoA, derivatives of 507 biosynthesis of 722 branched chain 381 cyclopropane-containing 399 essential 721 in lipids 380 names of, table 380 oxidation 511 pKa values of 380 stability of 589... 

Fatty acids containing one or more cyclopropane rings are present in many bacteria (p. 381).124 125 The extra carbon of the cyclopropane ring is added from S-adenosylmethionine (AdoMet) at the site of a cis double bond in a fatty acyl group of a phosphatidyle-thanolamine molecule in a membrane (Eq. 21-4).126/1263 The same type of intermediate carbocation can yield either a cyclopropane fatty acid (Eq. 21-4, step a) or a methenyl fatty acid (Eq. 21-4, step b). The latter can be reduced to a branched fatty acid. This is an alternative way of introducing methyl branches that is used by some bacteria.127... 

But chrysanthemic acid derivatives are by far not the only examples of cyclopropane-containing structures in nature. In fact, the highly strained three-membered carbocycle is virtually ubiquitous. It occurs, for example, in every green plant in the form of 1-aminocyclopropanecarboxylic acid (ACC) 2, a direct precursor to the plant hormone ethylene [3]. In addition, the cyclopropane unit is found in a variety of other natural products, inter alia in terpenes and in various cyclopropanated fatty acids [4]. The biochemical precursors of the latter are unsaturated fatty acids, and in view of the existence of polyunsaturated fatty... 

Cyclopropane containing fatty acids are found in bacterial membranes thus lac-tobacillic acid 141 has been isolated from Lactobacillus arabinosus, Brucella abortus and B. melitensis, Eq. (56) [188]. 

Fatty acids with trans or non-methylene-interrupted unsaturation occur naturally or are formed during processing for example, vaccenic acid (18 1 Hr) and the conjugated linoleic acid (CLA) rumenic acid (18 2 9tllc) are found in dairy fats. Hydroxy, epoxy, cyclopropane, cyclopropene acetylenic, and methyl branched fatty acids are known, but only ricinoleic acid (12(/f)-hydroxy-9Z-octadecenoic acid) (2) from castor oil is used for oleochemical production. OUs containing vernolic acid (12(5),13(/ )-epoxy-9Z-octadecenoic acid) (3) have potential for industrial use. 

Dunnick and O Leary [149] examined the lipid composition of a number of bacteria both sensitive and resistant to polymyxin and tetracycline. All fatty acid extracts from antibiotic resistant Gramnegative organisms contained higher concentrations of cyclopropane acids than the corresponding extracts from sensitive organisms. Thus, cyclopropane acids and unsaturated fatty acids appear to play a role in the integrity of the penetration barrier at least for polymyxin and tetracycline. 

The net addition to an olefin moiety of a bridging methylene group derived from the activated methyl fragment of 5-adenosylmethionine commonly occurs in the biosynthesis of cyclopropane-containing steroidal side chains and fatty acids, and has been best studied... 

Similar to the cases encountered in the biosynthesis of cyclopropane-containing fatty acids and phytosterols conventional alkylation of brassicasterol (102) with S-... 

Fatty acids containing cyclopropanes are relatively common constituents of bacterial and plant lipids where the precursors are obviously the corresponding olehnic fatty acids. Common olefinic loci are in Cjg and A Mn Cj g fatty acids and the subsequent... 

The accumulation of cyclopropane fatty acid-containing phospholipids is promoted in bacteria by low pH and low p02, conditions which attend entrance into stationary phase cultures. The conversion of olefin to cyclopropane alters membrane fluidity and probably other functional parameters as well and may be a physiological response to altered environmental conditions. 

C=0, -COOH, cyclopropane rings, methyl branches, and C=C bonds. Each species of Mycobacterium contains about two dozen different mycolic acids ° as well as other complex Csq-C fatty acids (see Eq. 21-5). Certain polyunsaturated fatty acids are essential in the human diet (see Box 21-B). One of these, arachidonic acid (which may be formed from dietary linoleic acid), serves as a precursor for the formation of the hormones known as prostaglandins and a series of related prostanoids. Lipids of animal origin also... 

AdoMet is also a precursor to the plant hormone, ethylene. A similar mechanism is probably involved in making rare fatty acids containing a cyclopropane ring. 

Fatty acids containing one or more cyclopropane rings are present in many bacteria (p. 381). The extra carbon of the cyclopropane ring is added from... 

Mycobacteria are rich in cyclopropane-containing fatty acids. These mycolic acids are major components of the cell walls and may account for 30% of the dry weight of the cells. The most abundant mycolic acid of M. tuberculosis consists of C52 fatty acid containing two cyclopropane rings joined via a Claisen-type condensation with a C25 carboxylate fatty acid (Eq. 21-... 

Some natural fatty acids contain a carbocyclic unit which may have three (cyclopropane and cyclo-propene acids), five (prostaglandins-see Section 1.4 and cyclopentene acids) or six carbon atoms (cyclohexane acids). Aspects of this topic have been reviewed (Christie, 1970 Lie Ken lie, 1979 and Badami and Patil, 1982). Other cyclic acids occur in tall oil (Section 3.3.36). 

Fatty acids in the 12-20 carbon chain-length range account for the majority of bacterial fatty acids. These are usually saturated or monounsaturated polyunsaturated fatty acids only occur in a few species, such as the gliding bacteria which accumulate large amounts of arachidonate (Fautz et al., 1979) or cyanobacteria which contain linoleate and linolenate. Reports of polyunsaturated fatty acids in bacteria should be treated with scepticism because of the ease with which bacteria can take up growth constituents which can include polyunsaturates. Besides the ubiquitous even-chain saturated and unsaturated fatty acids bacteria characteristically contain odd-chain and branched fatty acids as well as 3-hydroxy-and cyclopropane derivatives. These fatty acids are present in lipopolysaccharide, cell wall lipoprotein and lippteichoic acid as well as membrane glycerolipids (Table 3.209). 

The skeleton consists of a branched polymer of D-arabinose and D-galactose in a 5 2 ratio where about every tenth arabinose contains a mycolic acid esterified to the 5 -hydroxyl. These mycolic acids are 60-90 carbon fatty acids which are 2-branched and 3-hydroxylated. They may also contain cyclopropane rings, methyl branches and methoxy groups. In Nocardia similar arabinogalactan mycolates are present, known as nocardomycolic acids (40-60 carbons with a Ci4 or Ci6branch). In Corynebacterium spp., corynomycolic acids (28-40 carbons with a C14 branch) are found (Minnikin, 1982). 

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