Fatty acid synthesis pathways

P. putida grown with hexanoic acid contained approximately 75, 11, and 10 mol% of 3HHx,3HO, and 3HD units and also small amounts of four unsaturated repeating units. The mechanism for the formation of 3HO unit was investigated by 13C NMR study, which showed that the most of 3HO units found in this PHA were formed by the reaction of hexanoic acid with acetyl-CoA [53]. These results confirmed that P. putida produces 3HA units by fatty acid synthesis pathway, through a -oxidation and chain elongation process. 

The fatty acid synthesis pathway can be seen to occur in two parts. An initial priming stage in which acetyl-CoA is converted to malonyl-CoA by a carboxylation reaction (Figure 6.9) is followed by a series of reactions which occur on a multi-enzyme complex (MEC), which achieves chain elongation forming C16 palmitoyl-CoA. The whole process occurs in the cytosol. 

Two general classes of pheromone compound have been identified in moths, and these have some broad, although not uniform, associations with certain taxa. The polyene hydrocarbons and epoxides of various chain lengths are pheromones found in some subfamilies of the Geometridae and Noctuidae, and in the Arctiidae and Lymantridae (Millar, 2000). These compounds are probably derived from dietary Unoleic and linolenic acids. The other major class of pheromone compounds includes acetate, alcohols, and aldehydes, which are found in the Tortrici-dae, Pyralidae, Gelechiidae, Sessiidae, and Noctuidae. This class of compounds is derived from the insect s fatty acid synthesis pathway, with enzymatic modifications discussed above. Both classes of pheromone are broadly represented in the Noctuidae but are typically found in different subfamilies (Am et al., 1992,2003). 

Fatty acids are the building blocks of TAG. More than 90 percent of fatty acids have an even number of carbon atoms, and are in aliphatic chains ranging from 4 to 22 carbons in length. The major fatty acid synthesis pathway is production of stearic acid (18 carbons) after which separate desaturase systems introduce 1, 2, or 3 unsaturated (double) bonds. Additional enzymes become active in elongating the chain as needed. Shorter fatty acids also are produced. Trace amounts of odd-number carbon fatty acids are found in most fats, and also have been synthesized for research purposes. Microorganisms frequently produce odd-number carbon fatty acids, with heptadecenoic (17 carbon) acid a major component of Candida tropicalis yeast fat. Up to 8 percent C17 fatty acids have been found in milk and meat fats of ruminants (cattle, sheep, goats) and are of rumen microbe origin. 

Figure 4.46 shows the first step (acetyl-CoA carboxylase catalyzed) in the fatty acid synthesis pathway. The enzyme is biolin-requiring, and the product is maJonyl-CoA. Note that the activities of about 1(X) different enzymes have been found to be controlled by phosphorylation (Shacter et al, 1986). In all cases, the phosphorylation is re ersible. The phosphate donor may be ATP or GTP. 

FIGURE 4.46 First Step of the fatty acid synthesis pathway. 

Other Players in the Fatty Acid Synthesis Pathway... 

Milgraum, L. Z., Witters, L. A., Pasternack, G. R. and Kuhajda, F. P., Enzymes of the fatty acid synthesis pathway are highly expressed in in situ breast carcinoma, Clin Cancer Res 3 (1997) 2115-2120. 

Swinnen, J. V., Vanderhoydonc, F., Elgamal, A. A., Eelen, M., Vercaeren, I., Ionian, S., Van Poppel, H., Baert, L., Goossens, K., Heyns, W. and Verhoeven, G., Selective activation of the fatty acid synthesis pathway in human prostate cancer, Int J Cancer 88 (2000b) 176-179. 

Fig. 11. Genetic engineering of rapeseed oil. A high level of lauric acid was achieved by expressing a medium-chain acyl-ACP thioesterase (MCTE) from California Bay in the transgenic seeds. This enzyme intercepts the fatty acid synthesis pathway at 12 carbons and hydrolyzes the fatty acid from its ACP carrier. MoI% of major fatty acids in a typical canola cultivar are compared to the composition achieved through genetic engineering.

Erythromycin is a polyketide antibiotic made via a modification of the fatty acid synthesis pathway in the bacterium Saccharopolyspora erythraea. It acts by binding to a specific site on the 23 S rRNA and blocking elongation by q... 

Variant Fatty Acid Synthesis Pathways that Lead to Antibiotics (Figure 18.35) Polyketides... 

You, M., M. Fischer, M.A. Deeg, and D.W. Grahh. 2002. Ethanol induces fatty acid synthesis pathways by activation of sterol regnlatory element-binding protein (SREBP). 

You M, Fischer M, Deeg MA, Crabb DW. Ethanol induces fatty acid synthesis pathways... 

Fig. 3.5. Biosynthesis of unsaturated fatty acids. Synthesis pathways a, c, g in higher plants a, c, g and a, c, d, f in algae a, b and d, f (main pathway for arachidonic acid) or e, f in mammals...

I Sanyal, SL L.ee, DH Flint. Biosynthesis of pimeloyl-CoA, a biotin precursor in E. coli, follows a modified fatty acid synthesis pathway C-labeling studies. J Am Chem Soc 116 2637-2638, 1994. 

FIGURE 11.5 Biosynthetic pathway of MCL-PHAs and LCL-PHAs in Pseudomonas aeruginosa using fatty acid synthesis pathway. Enzymes 1 Ketoacyl-ACP synthase, 2 Ketoacyl-ACP reductase, 3 3-Hydroxyacyl-ACP dehydratase, 4 Enoyl-ACP reductase, 5 3-Hydroxyacyl-ACP-CoA transacylase and 6 PHA polymerase (Tiimn and Steinbuchel, 1990 Steinbuchel, 1996 Singh and Mallick, 2008 Singh and Mallick, 2009b). 

Fenoxaprop Aryloxypropionate Acetyl CoA carbox-ylase (ACCase) Inhibition of acetyl CoA carbox-ylase in fatty acid synthesis pathway 1984 Post- em gence Cereals Grasses, 200-500... 

Inhibition of acetyl CoA carboxylase in fatty acid synthesis pathway Acetyl CoA carboxylase (ACCase) 19... 

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