Note: a dashed line (without arrowheads) between two compound names is meant to imply that the two names are just different instantiations of the same compound -- i.e. one may be a specific name and the other a general name, or they may both represent the same compound in different stages of a polymerization-type pathway. This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
|Superclasses:||Degradation/Utilization/Assimilation → Fatty Acid and Lipids Degradation → Fatty Acids Degradation|
The catabolism of fatty acids proceeds via several routes, which depend on the length of the acids, whether the number of carbons is odd or even, and whether they are saturated or unsaturated. This pathway represents the "core" cycle of β-oxidation, a mechanism that removes two carbon atoms with each turn of the cycle.
Saturated fattty acids that are routed into this core pathway are processed until only two or three carbons remain. When even-numbered fatty acids are broken down, the final product is the two-carbon compound acetyl-CoA, which is a basic intermediate of central metabolism, and can be routed into the TCA cycle for complete catabolism or routed into the glyoxylate cycle to be used for biosynthesis. When odd number fatty acids are broken down, the final product of the pathway is the three-carbon compound propanoyl-CoA, which in Escherichia coli is carboxylated to methylmalonyl-CoA and converted to succinyl-CoA (see propanoyl CoA degradation I).
Unsaturated fatty acids with cis double bonds located at odd-numbered carbon atoms enter the main pathway after a modification (see fatty acid β-oxidation III (unsaturated, odd number)). When cis double bonds are located at even-numbered carbon atoms (such as in linoleate), the acids are modified by a different route (see unsaturated, even numbered fatty acid β-oxidation).
Although enzymes of the pathway handle both short and long chain fatty acids, it is the long chain compounds that induce the enzymes of the pathway [Clark81].
The pathway under anaerobic conditions
In the facultative anaerobic bacterium Escherichia coli the pathway can proceed under anaerobic conditions [Campbell03]. The enzymatic steps are identical, and the main difference is that the product of the pathway, acetyl-CoA, is oxidized using fumarate as the terminal electron acceptor [MorganKiss04]. However, a different set of enzymes is active under anaerobic conditions. In the anaerobic pathway FadI, FadJ, and FadK serve functions parallel to those of FadA, FadB, and FadD in the aerobic pathway [Campbell03]. In contrast to the aerobic pathway, octanoate and decanoate can serve as substrates for the anaerobic fatty acid oxidation pathway [Campbell03].
Unification Links: EcoCyc:FAO-PWY
Campbell03: Campbell JW, Morgan-Kiss RM, E Cronan J (2003). "A new Escherichia coli metabolic competency: growth on fatty acids by a novel anaerobic beta-oxidation pathway." Mol Microbiol 47(3);793-805. PMID: 12535077
Abe93: Abe H, Ohtake A, Yamamoto S, Satoh Y, Takayanagi M, Amaya Y, Takiguchi M, Sakuraba H, Suzuki Y, Mori M (1993). "Cloning and sequence analysis of a full length cDNA encoding human mitochondrial 3-oxoacyl-CoA thiolase." Biochim Biophys Acta 1216(2);304-6. PMID: 8241273
Antonenkov97: Antonenkov VD, Van Veldhoven PP, Waelkens E, Mannaerts GP (1997). "Substrate specificities of 3-oxoacyl-CoA thiolase A and sterol carrier protein 2/3-oxoacyl-CoA thiolase purified from normal rat liver peroxisomes. Sterol carrier protein 2/3-oxoacyl-CoA thiolase is involved in the metabolism of 2-methyl-branched fatty acids and bile acid intermediates." J Biol Chem 272(41);26023-31. PMID: 9325339
Arnauld: Arnauld S, Fidaleo M, Clemencet MC, Chevillard G, Athias A, Gresti J, Wanders RJ, Latruffe N, Nicolas-Frances V, Mandard S "Modulation of the hepatic fatty acid pool in peroxisomal 3-ketoacyl-CoA thiolase B-null mice exposed to the selective PPARalpha agonist Wy14,643." Biochimie 91(11-12);1376-86. PMID: 19772884
Begrends88: Begrends, Wilke, Engeland, Kurt, Kindl, Helmut (1988). "Characterization of two forms of the multifunctional protein acting in fatty acid beta-oxidation." Arch Biochem Biophys, 263(1): 161-1691.
Behrends88: Behrends W, Engeland K, Kindl H (1988). "Characterization of two forms of the multifunctional protein acting in fatty acid beta-oxidation." Arch Biochem Biophys 263(1);161-9. PMID: 3130799
Beloin04: Beloin C, Valle J, Latour-Lambert P, Faure P, Kzreminski M, Balestrino D, Haagensen JA, Molin S, Prensier G, Arbeille B, Ghigo JM (2004). "Global impact of mature biofilm lifestyle on Escherichia coli K-12 gene expression." Mol Microbiol 51(3);659-74. PMID: 14731270
Black92: Black PN, DiRusso CC, Metzger AK, Heimert TL (1992). "Cloning, sequencing, and expression of the fadD gene of Escherichia coli encoding acyl coenzyme A synthetase." J Biol Chem 1992;267(35);25513-20. PMID: 1460045
Black97: Black PN, Zhang Q, Weimar JD, DiRusso CC (1997). "Mutational analysis of a fatty acyl-coenzyme A synthetase signature motif identifies seven amino acid residues that modulate fatty acid substrate specificity." J Biol Chem 272(8);4896-903. PMID: 9030548
Bout91: Bout A, Franse MM, Collins J, Blonden L, Tager JM, Benne R (1991). "Characterization of the gene encoding human peroxisomal 3-oxoacyl-CoA thiolase (ACAA). No large DNA rearrangement in a thiolase-deficient patient." Biochim Biophys Acta 1090(1);43-51. PMID: 1679347
Brueton92: Brueton LA, van Herwerden L, Chotai KA, Winter RM (1992). "The mapping of a gene for craniosynostosis: evidence for linkage of the Saethre-Chotzen syndrome to distal chromosome 7p." J Med Genet 29(10);681-5. PMID: 1433226
Cao08: Cao W, Liu N, Tang S, Bao L, Shen L, Yuan H, Zhao X, Lu H (2008). "Acetyl-Coenzyme A acyltransferase 2 attenuates the apoptotic effects of BNIP3 in two human cell lines." Biochim Biophys Acta 1780(6);873-80. PMID: 18371312
Cao98: Cao Y, Traer E, Zimmerman GA, McIntyre TM, Prescott SM (1998). "Cloning, expression, and chromosomal localization of human long-chain fatty acid-CoA ligase 4 (FACL4)." Genomics 49(2);327-30. PMID: 9598324
Chen91a: Chen GL, Balfe A, Erwa W, Hoefler G, Gaertner J, Aikawa J, Chen WW (1991). "Import of human bifunctional enzyme into peroxisomes of human hepatoma cells in vitro." Biochem Biophys Res Commun 178(3);1084-91. PMID: 1651711
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