Fatty cyclopropane

Cyclopropane fatty Cyclopropane synthase E. coli Tobacco... 

FIGURE 8.2 Structures of two unusual fatty acids lactobacillic acid, a fatty acid coutaiuiug a cyclopropane ring, and tuberculostearic acid, a brauched-chaiu fatty acid. 

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. 

Tipton CL, NM Al-Shathir (1974) The metabolism of cyclopropane fatty acids by Tetrahymena pyriformis. J Biol Chem 249 886-889. 

FIGURE 4 Ectocarpene as the product of a [3.3]-sigmatropic rearrangement. The fatty acid accommodates to the active center of the enzyme in a U-shaped fashion. Decarboxylation in conjunction with loss of the C(8) HR hydrogen atom yields, after cyclization between C(4) and C(6) of the precursor, the thermolabile (lS,2R)-cyclopropane. A subsequent spontaneous [3.3]-sigmatropic rearrangement (Cope rearrangement) proceeds via the cis-endo transition state and yields (6S )-ectocarpene. 

FIGURE 6 Speculative mechanism of Crl hydrocarbon biosynthesis from fatty acid hydroperoxides in algae. Homolytic cleavage of the hydroperoxide is assumed to give an allyl radical, which cyclizes to the thermolabile (1S,2R)-cyclopropane. The sequence is terminated by transfer of a hydrogen radical from C(16) to the -X-0 function. The cyclopropane rearranges to (6S)-ectocarpene as shown in Figure 4. 

Among these were a cyclopropane fatty acid from Sterculia foetida (Sterculiaceae) seed oil (0.1%) and cyanolipids from Koelreuteri a... 

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,... 

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... 

Nonhydroxylated and hydroxylated fatty acids (C10-C18) comprise the hydrophobic region of lipid A s. Among these, cyclopropane and, in general, unsaturated fatty acids are lacking. In the following, procedures are described which were applied for the determination of the nature, quantity and binding site of fatty acids present in Salmonella lipid A (39). 

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]. 

The formation of by-products is also brought about by the presence of a cyclopropane ring in the molecule of the substrate, e.g., some bacterial fatty acids [7]. The aggressive methanol-BF3 reagent must then be replaced with a milder reagent, e.g., 10% (w/v)... 

Will the melting point of lactobacillic acid (Ci9H36C>2, a cyclopropane fatty acid) be higher or lower than that of the linear, saturated fatty acid of the same chain length ... 

The melting point will be lower the cyclopropane group decreases the tendency of an array of molecules to pack regularly. The melting points of lactobacillic acid and the 19 0 fatty acid are 28°C and 69°C, respectively. 

Other modifications of the hydrocarbon chain of fatty acids, such as hydroxylation or introduction of a cyclopropane, cyclopropene or epoxy ring, could be identified and located... 

Bao XM, Katz S, Pollard M, Ohlrogge J. Carbocyclic fatty acids in plants biochemical and molecular genetic characterization of cyclopropane fatty acid synthesis of Sterculia foetida. Proc. Natl. Acad. Sci. U.S.A. 2002 99 7171-7177. 

Cyclic fatty acids with a carbon ring alone or at the end of the alkyl chain occur naturally in plants, especially in certain seed oils and in microorganisms. Cyclopropane fatty acids are reported occasionally from marine animals and may be synthesized by symbiotic bacteria. In addition, a variety of carbocyclic structures are formed from methylene-intermpted polyenes during food processing. 

The cyclopropane fatty acid, cw-11,12-methylene-octadeca-noic acid, was reported first for Lactobacillus arabinosus and was given the trivial name lactobacillic acid. By now, fatty acids with a mid-chain cyclopropane group have been found in many bacterial species, including aerobic, anaerobic. Gram-negative,... 

Iwig DF, Grippe AT, McIntyre TA, Booker SJ. Isotope and elemental effects indicate a rate-limiting methyl transfer as the initial step in the reaction catalyzed by Escherichia coli cyclopropane fatty acid synthase. Biochemistry 2004 43 13510-13524. 

Courtois E, Ploux O. Escherichia coli cyclopropane fatty acid synthase is a bound bicarbonate ion the active-site base Biochemistry 2005 44 13583-13590. 

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. 

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