If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
Locations of Mapped Genes:
Synonyms: palmitoleic acid biosynthesis I, palmitoleate biosynthesis (anaerobic)
|Superclasses:||Biosynthesis → Fatty Acid and Lipid Biosynthesis → Fatty Acid Biosynthesis → Unsaturated Fatty Acid Biosynthesis → Palmitoleate Biosynthesis|
In E. coli, two unsaturated fatty acids, palmitoleate and cis-vaccenate, together comprise about one-half of the total fatty acid content of the organism. Palmitate, palmitoleate and cis-vaccenate make up the bulk of the fatty acids found in E. coli membranes [Magnuson93].
About This Pathway
In E. coli, the extension of a cis-δ-5-decenoyl-[acp] to a palmitoleoyl-[acp] is believed to be catalyzed primarily by KASI. Inactivation of this enzyme leads to a lack of unsaturated fatty acids [Cronan69]. On the other hand, overexpression of KASI leads to the overproduction of cis-vaccenate [deMendoza83].
It has been shown that the basal ratio of saturated to unsaturated fatty acids in E. coli is controlled by the level of two enzymes - β-hydroxyacyl-ACP dehydratase/isomerase (fabA) and KASI [Magnuson93]. The former introduces unsaturation (see (5Z)-dodec-5-enoate biosynthesis), while the other elongates the unsaturated fatty acid to the level of a palmitoleoyl-[acp] (this pathway).
Additional control over this ratio is provided by temperature. The proportion of unsaturated fatty acids is known to increase in E. coli with lower growth temperature, a phenomenon found in most organisms that provides a mechanism for adjusting the lipid phase transition of the membrane phospholipids to differing temperatures. It has been shown that KASII which is responsible for the further elongation of the unsaturated fatty acids to the final level of cis-vaccenate (see cis-vaccenate biosynthesis), is more active at low temperatures (relative to the overall rate of fatty acid synthesis) than at high temperatures [Garwin80]. This relative increase results in the production of cis-vaccenate rather than palmitoleate. Because the former (but not the later) can be incorporated into both positions of sn-glycerol 3-phosphate, the synthesis of di-unsaturated phospholipids occurs and the thermotrophic phase transition of the membrane phospholipids is lowered [Garwin80a].
Casey94: Casey WM, Gibson KJ, Parks LW (1994). "Covalent attachment of palmitoleic acid (C16:1 delta 9) to proteins in Saccharomyces cerevisiae. Evidence for a third class of acylated proteins." J Biol Chem 269(3);2082-5. PMID: 8294460
deMendoza83: de Mendoza D, Klages Ulrich A, Cronan JE (1983). "Thermal regulation of membrane fluidity in Escherichia coli. Effects of overproduction of beta-ketoacyl-acyl carrier protein synthase I." J Biol Chem 258(4);2098-101. PMID: 6337151
Garwin80: Garwin JL, Klages AL, Cronan JE (1980). "Structural, enzymatic, and genetic studies of beta-ketoacyl-acyl carrier protein synthases I and II of Escherichia coli." J Biol Chem 1980;255(24);11949-56. PMID: 7002930
Garwin80a: Garwin JL, Klages AL, Cronan JE (1980). "Beta-ketoacyl-acyl carrier protein synthase II of Escherichia coli. Evidence for function in the thermal regulation of fatty acid synthesis." J Biol Chem 1980;255(8);3263-5. PMID: 6988423
Baldock96: Baldock C, Rafferty JB, Sedelnikova SE, Baker PJ, Stuitje AR, Slabas AR, Hawkes TR, Rice DW (1996). "A mechanism of drug action revealed by structural studies of enoyl reductase." Science 274(5295);2107-10. PMID: 8953047
Barnes68: Barnes EM, Wakil SJ (1968). "Studies on the mechanism of fatty acid synthesis. XIX. Preparation and general properties of palmityl thioesterase." J Biol Chem 1968;243(11);2955-62. PMID: 4871199
Bergler94: Bergler H, Wallner P, Ebeling A, Leitinger B, Fuchsbichler S, Aschauer H, Kollenz G, Hogenauer G, Turnowsky F (1994). "Protein EnvM is the NADH-dependent enoyl-ACP reductase (FabI) of Escherichia coli." J Biol Chem 1994;269(8);5493-6. PMID: 8119879
Bergler96: Bergler H, Fuchsbichler S, Hogenauer G, Turnowsky F (1996). "The enoyl-[acyl-carrier-protein] reductase (FabI) of Escherichia coli, which catalyzes a key regulatory step in fatty acid biosynthesis, accepts NADH and NADPH as cofactors and is inhibited by palmitoyl-CoA." Eur J Biochem 242(3);689-94. PMID: 9022698
Cao10a: Cao Y, Yang J, Xian M, Xu X, Liu W (2010). "Increasing unsaturated fatty acid contents in Escherichia coli by coexpression of three different genes." Appl Microbiol Biotechnol 87(1);271-80. PMID: 20135119
DiazMejia09: Diaz-Mejia JJ, Babu M, Emili A (2009). "Computational and experimental approaches to chart the Escherichia coli cell-envelope-associated proteome and interactome." FEMS Microbiol Rev 33(1);66-97. PMID: 19054114
Escaich11: Escaich S, Prouvensier L, Saccomani M, Durant L, Oxoby M, Gerusz V, Moreau F, Vongsouthi V, Maher K, Morrissey I, Soulama-Mouze C (2011). "The MUT056399 inhibitor of FabI is a new antistaphylococcal compound." Antimicrob Agents Chemother 55(10);4692-7. PMID: 21825292
Feng09: Feng Y, Cronan JE (2009). "Escherichia coli unsaturated fatty acid synthesis: complex transcription of the fabA gene and in vivo identification of the essential reaction catalyzed by FabB." J Biol Chem 284(43);29526-35. PMID: 19679654
Goh09: Goh S, Boberek JM, Nakashima N, Stach J, Good L (2009). "Concurrent growth rate and transcript analyses reveal essential gene stringency in Escherichia coli." PLoS One 4(6);e6061. PMID: 19557168
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