If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
|Superclasses:||Biosynthesis → Carbohydrates Biosynthesis|
Some taxa known to possess this pathway include : Escherichia coli K-12 substr. MG1655
Expected Taxonomic Range: Proteobacteria
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, Majdalani05a].
Unification Links: EcoCyc:COLANSYN-PWY
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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