If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
Locations of Mapped Genes:
|Superclasses:||Biosynthesis → Carbohydrates Biosynthesis|
Colanic acid, also known as the M antigen, is an extracellular polysaccharide found in Enterobacteriaceae. It is a polyanionic heteropolysaccharide containing a repeat unit with D-glucose, L-fucose, D-galactose, and D-glucuronate sugars that are nonstoichiometrically decorated with O-acetyl and pyruvate side chains [Grant69, Garegg71]. The sugars need to be activated in the form of nucleotide sugars (UDP-α-D-glucose, GDP-β-L-fucose, UDP-α-D-galactose and UDP-α-D-glucuronate, respectively) prior to their assembly [Stevenson96, Stout96].
The colanic acid polysaccharide repeat is assembled on the membrane lipid all-trans-dodecaprenyl diphosphate by a series of glycosyl transferases on the cytoplasmic face of the inner membrane, after which the single repeat is flipped to the periplasmic side and polymerized by the Wzy-dependent pathway (reviewed in [Raetz02] and [Whitfield06]). Subsequently, the polymer is believed to be cleaved from the all-trans-dodecaprenyl diphosphate anchor, transported across the periplasm, and excreted into the extracellular space, although this process is not well understood.
Colanic acid biosynthesis has been linked to a cluster of 19 genes, which were named wca [Stevenson96, Stout96]. This gene cluster is tightly regulated by a complex signal transduction cascade governed by the rcs (regulator of capsule synthesis) phosphorelay system [Gottesman85, Majdalani05].
Subpathways: GDP-L-fucose biosynthesis I (from GDP-D-mannose) , GDP-mannose biosynthesis , UDP-α-D-glucuronate biosynthesis (from UDP-glucose) , UDP-D-galactose biosynthesis , UDP-glucose biosynthesis
Created 02-Dec-1997 by Pellegrini-Toole A , Marine Biological Laboratory
Revised 29-May-2008 by Caspi R , SRI International
Revised 13-Jun-2008 by Keseler I , SRI International
Revised 15-Aug-2013 by Caspi R , SRI International
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Gottesman85: Gottesman S, Trisler P, Torres-Cabassa A (1985). "Regulation of capsular polysaccharide synthesis in Escherichia coli K-12: characterization of three regulatory genes." J Bacteriol 162(3);1111-9. PMID: 3888955
Stevenson96: Stevenson G, Andrianopoulos K, Hobbs M, Reeves PR (1996). "Organization of the Escherichia coli K-12 gene cluster responsible for production of the extracellular polysaccharide colanic acid." J Bacteriol 1996;178(16);4885-93. PMID: 8759852
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Andrianopoulos98: Andrianopoulos K, Wang L, Reeves PR (1998). "Identification of the fucose synthetase gene in the colanic acid gene cluster of Escherichia coli K-12." J Bacteriol 1998;180(4);998-1001. PMID: 9473059
Aoyama94b: Aoyama K, Haase AM, Reeves PR (1994). "Evidence for effect of random genetic drift on G+C content after lateral transfer of fucose pathway genes to Escherichia coli K-12." Mol Biol Evol 1994;11(6);829-38. PMID: 7815923
Arabshahi88: Arabshahi A, Flentke GR, Frey PA (1988). "Uridine diphosphate galactose 4-epimerase. pH dependence of the reduction of NAD+ by a substrate analog." J Biol Chem 263(6);2638-43. PMID: 3277958
Arrecubieta94: Arrecubieta C, Lopez R, Garcia E (1994). "Molecular characterization of cap3A, a gene from the operon required for the synthesis of the capsule of Streptococcus pneumoniae type 3: sequencing of mutations responsible for the unencapsulated phenotype and localization of the capsular cluster on the pneumococcal chromosome." J Bacteriol 176(20);6375-83. PMID: 7929009
Bauer91: Bauer AJ, Rayment I, Frey PA, Holden HM (1991). "The isolation, purification, and preliminary crystallographic characterization of UDP-galactose-4-epimerase from Escherichia coli." Proteins 9(2);135-42. PMID: 2008433
Bauer92: Bauer AJ, Rayment I, Frey PA, Holden HM (1992). "The molecular structure of UDP-galactose 4-epimerase from Escherichia coli determined at 2.5 A resolution." Proteins 12(4);372-81. PMID: 1579570
Berger01: Berger E, Arabshahi A, Wei Y, Schilling JF, Frey PA (2001). "Acid-base catalysis by UDP-galactose 4-epimerase: correlations of kinetically measured acid dissociation constants with thermodynamic values for tyrosine 149." Biochemistry 40(22);6699-705. PMID: 11380265
Bhattacharyya99: Bhattacharyya U, Dhar G, Bhaduri A (1999). "An arginine residue is essential for stretching and binding of the substrate on UDP-glucose-4-epimerase from Escherichia coli. Use of a stacked and quenched uridine nucleotide fluorophore as probe." J Biol Chem 274(21);14573-8. PMID: 10329648
Bingham87: Bingham AH, Busby SJ (1987). "Translation of galE and coordination of galactose operon expression in Escherichia coli: effects of insertions and deletions in the non-translated leader sequence." Mol Microbiol 1(1);117-24. PMID: 2838723
Blackburn76: Blackburn P, Ferdinand W (1976). "The concerted inactivation of Escherichia coli uridine diphosphate galactose 4-epimerase by sugar nucleotide together with a free sugar." Biochem J 155(2);225-9. PMID: 779771
Brautaset98: Brautaset T, Petersen S, Valla S (1998). "An experimental study on carbon flow in Escherichia coli as a function of kinetic properties and expression levels of the enzyme phosphoglucomutase." Biotechnol Bioeng 58(2-3);299-302. PMID: 10191405
Burke93: Burke JR, Frey PA (1993). "The importance of binding energy in catalysis of hydride transfer by UDP-galactose 4-epimerase: a 13C and 15N NMR and kinetic study." Biochemistry 1993;32(48);13220-30. PMID: 8241177
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