If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
Locations of Mapped Genes:
Synonyms: glyoxylate bypass, glyoxylate shunt
|Superclasses:||Generation of Precursor Metabolites and Energy|
The glyoxylate cycle is a sequence of anaplerotic reactions that enables an organism to use substrates that enter central carbon metabolism at the level of acetyl-CoA as the sole carbon source. Such substrates include fatty acids, alcohols, and esters (often the products of fermentation), as well as waxes, alkenes, and methylated compounds.
The pathway is essentially a modified version of the TCA cycle I (prokaryotic) that bypasses those steps in the cycle that lead to a loss of CO2. The glyoxylate cycle uses a two-step bypass. The first key enzyme, isocitrate lyase (EC 18.104.22.168), converts D-threo-isocitrate to form succinate and glyoxylate. The second key enzyme, malate synthase A (EC 22.214.171.124), condenses glyoxylate and another molecule of acetyl-CoA to form (S)-malate. The subsequent oxidation of malate regenerates the initial acetyl-CoA acceptor molecule of the TCA cycle, oxaloacetate. In this way any intermediate of the TCA cycle can be withdrawn from the cycle and used for cell carbon biosynthesis.
In Escherichia coli the pathway is active when growth on two-carbon compounds requires conservation of four-carbon TCA intermediates. Two acetyl-CoA are taken up per turn. The glyoxylate cycle is repressed during growth on glucose and induced by growth on acetate [Cortay89, Walsh84, LaPorte84, Nimmo84].
Acetyl-CoA is generated by acetate conversion to acetyl-CoA or by β oxidation of fatty acids.
Cortay89: Cortay JC, Bleicher F, Duclos B, Cenatiempo Y, Gautier C, Prato JL, Cozzone AJ (1989). "Utilization of acetate in Escherichia coli: structural organization and differential expression of the ace operon." Biochimie 71(9-10):1043-1049. PMID: 2512996
Nimmo84: Nimmo GA, Nimmo HG (1984). "The regulatory properties of isocitrate dehydrogenase kinase and isocitrate dehydrogenase phosphatase from Escherichia coli ML308 and the roles of these activities in the control of isocitrate dehydrogenase." Eur J Biochem 1984;141(2);409-14. PMID: 6329757
Walsh84: Walsh K, Koshland DE (1984). "Determination of flux through the branch point of two metabolic cycles. The tricarboxylic acid cycle and the glyoxylate shunt." J Biol Chem 1984;259(15);9646-54. PMID: 6378912
Al12: Al Mamun AA, Lombardo MJ, Shee C, Lisewski AM, Gonzalez C, Lin D, Nehring RB, Saint-Ruf C, Gibson JL, Frisch RL, Lichtarge O, Hastings PJ, Rosenberg SM (2012). "Identity and function of a large gene network underlying mutagenic repair of DNA breaks." Science 338(6112);1344-8. PMID: 23224554
Anderson88c: Anderson DH, Duckworth HW (1988). "In vitro mutagenesis of Escherichia coli citrate synthase to clarify the locations of ligand binding sites." J Biol Chem 1988;263(5);2163-9. PMID: 3276685
Anstrom03: Anstrom DM, Kallio K, Remington SJ (2003). "Structure of the Escherichia coli malate synthase G:pyruvate:acetyl-coenzyme A abortive ternary complex at 1.95 A resolution." Protein Sci 12(9);1822-32. PMID: 12930982
Blank02: Blank L, Green J, Guest JR (2002). "AcnC of Escherichia coli is a 2-methylcitrate dehydratase (PrpD) that can use citrate and isocitrate as substrates." Microbiology 148(Pt 1);133-46. PMID: 11782506
Brock02: Brock M, Maerker C, Schutz A, Volker U, Buckel W (2002). "Oxidation of propionate to pyruvate in Escherichia coli. Involvement of methylcitrate dehydratase and aconitase." Eur J Biochem 269(24);6184-94. PMID: 12473114
Calderon09: Calderon IL, Elias AO, Fuentes EL, Pradenas GA, Castro ME, Arenas FA, Perez JM, Vasquez CC (2009). "Tellurite-mediated disabling of [4Fe-4S] clusters of Escherichia coli dehydratases." Microbiology 155(Pt 6);1840-6. PMID: 19383690
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
Duckworth87: Duckworth HW, Anderson DH, Bell AW, Donald LJ, Chu AL, Brayer GD (1987). "Structural basis for regulation in gram-negative bacterial citrate synthases." Biochem Soc Symp 1987;54;83-92. PMID: 3333000
Else88: Else AJ, Danson MJ, Weitzman PD (1988). "Models of proteolysis of oligomeric enzymes and their applications to the trypsinolysis of citrate synthases." Biochem J 1988;254(2);437-42. PMID: 3140803
Fernley81: Fernley RT, Lentz SR, Bradshaw RA (1981). "Malate dehydrogenase: isolation from E. coli and comparison with the eukaryotic mitochondrial and cytoplasmic forms." Biosci Rep 1(6);497-507. PMID: 7028159
Geck99: Geck MK, Kirsch JF (1999). "A novel, definitive test for substrate channeling illustrated with the aspartate aminotransferase/malate dehydrogenase system." Biochemistry 38(25);8032-7. PMID: 10387047
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