Fatty acid pathways

Capsaicinoids Are Products of the Phenylpropanoid Pathway and the Branched Chain Fatty Acid Pathway... 

Stored under continuous light, and placental extracts from non-pungent fruit could synthesize capsaicinoids if vanillylamine and isocapric acid are provided. Together, these results raise the possibility that the gene product at Pml is a regulatory gene or a structural gene upstream in either the phenylpropanoid pathway or the branched chain fatty acid pathway and not capsaicinoid synthase. 

Initial investigations into the biosynthesis of the curcuminoids and gingerols were performed many years ago (Denniff and Whiting, 1976 Macleod and Whiting, 1979 Denniff et al., 1980). These initial radiotracer feeding studies suggested that these compounds were derived from intermediates in the phenylpropanoid pathways that were condensed with other molecules, derived in turn from the acetate and short-and medium-chain fatty acid pathways. 

Guiet et al. (2003) demonstrated that deuterium (2H) distribution in fatty acids was non-statistical and could be related to isotopic discrimination during chain extension and desaturation. Petroselinic acid (C18 1A6) (Fig. 21.4), a fatty acid characteristic of the seeds of the Apiaceae, has been shown to be biosynthesized from palmitoyl-ACP (C16 0) by two steps, catalysed by a dedicated A4-desaturase and an elongase. The isotopic profile resulting from this pathway is similar to the classical plant fatty acid pathway, but the isotopic fingerprint from both the desaturase and elongase steps shows important differences relative to oleic and linoleic acid biosynthesis. 

The fatty acid pathway or, as we should call it now, the acyl polymalonate pathway, also gives rise to an inexhaustible variety of aromatic and other compounds belonging to the family of the polyketides. You saw in Chapter 50 how the shikimic acid pathway makes aromatic compounds but the compounds below are from the polyketide route. 

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... 

Because of Its structural similarity to acetate. It is not surprising that cyclopropanecarboxyllc acid (from the mltlclde cycloprate) Is Incorporated readily Into normal fatty acid pathways. Six homologous (i>-cyclopropyl fatty acids were identified from treatment of rats, dogs, and a cow with cycloprate (7-10). Generally, these (it-cyclopropyl fatty acids were not free, but rather were esterified to produce modified hybrid lipids (vide Infra ). 

Labeling studies suggest that pimeloyl CoA is synthesized by a modified fatty acid pathway (Fig. 26) [117, 123, 124]. Cell free enzymatic activity has not been reported. Pimeloyl CoA is also synthesized from pimelic acid in Bacillus sphaericus [125]. 

Brefeldins A (4.104) and B, obtained from Penicillium brefeldianum and which also possess a cyclopentane ring, have a wide spectrum of biological activity, including antiviral and cytotoxic effects. Brefeldin A has been shown to incorporate acetate and specifically [9- C]palmitic acid, suggesting that it is biosynthesized by a fatty acid pathway. However, other macrolactones such as curvularin appear to be biosynthesized by a polyketide pathway. 

Rappleye CA, Tagawa A, Le BotN, Ahringer J, Aroian RV (2003) Involvement of fatty acid pathways and cortical interaction of the pronuclear complex in Caenorhabditis elegans embryonic polarity. BMC Dev Biol 3 8... 

There are no data concerning the biosynthesis of pyrrolidides found in Solanales species. However, it may be assumed that it involves again the A/-methyl-A -pyrrolinium unit since (i) the conioidines are hygroline derivatives and (ii) the convolvulaceous metabolites show strong structural similarity to pyrrohdine-type nicotinoids. The acyl moieties apparently come from the fatty acid pathway. The esterilying acids of the conioidines are derivatives of L-isoleucine. 

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