Taxonomic group: bacteria / Proteobacteria
(Phylum: Proteobacteria)
Associated disease: infection due to Escherichia coli [ICD11:
XN6P4 
]
NCBI PubMed ID: 8573097Journal NLM ID: 2984726RPublisher: London, UK : Published by Portland Press on behalf of the Biochemical Society
Institutions: Department of Medical and Physiological Chemistry, University of Uppsala, Sweden
The capsular polysaccharide from Escherichia coli K4 consists of a chondroitin ([GlcA(β1→3)GalNAc(β1→4)]n) backbone, to which β-fructofuranose units are linked to C-3 of D-glucuronic acid (GlcA) residues. Removal of the fructose units by mild acid hydrolysis provided a substrate for the GlcA C-5 epimerase, which is involved in the generation of L-iduronic acid (IdoA) units during dermatan sulphate biosynthesis. Incubation of this substrate with solubilized fibroblast microsomal enzyme in the presence of 3H2O resulted in the incorporation of tritium at C-5 of hexuronyl units. A Km of 67 x 10(-6) M hexuronic acid (equivalent to disaccharide units) was determined, which is similar to that (80 x 10(-6) M) obtained for dermatan (desulphated dermatan sulphate). Vmax was about 4 times higher with dermatan than with the K4 substrate. A defructosylated K4 polysaccharide isolated after incubation of bacteria with D-[5-3H]glucose released 3H2O on reaction with the epimerase, and thus could be used to assay the enzyme. Incubation of a K4 substrate with solubilized microsomal epimerase for 6 h in the presence of 3H2O resulted in the formation of about 5% IdoA and approximately equal amounts of 3H in GlcA and IdoA. A corresponding incubation of dermatan yielded approx. 22% GlcA, which contained virtually all the 3H label. These results are tentatively explained in terms of a two-base reaction mechanism, involving a monoprotic L-ido-specific base and a polyprotic D-gluco-specific base. Most of the IdoA residues generated by the enzyme occurred singly, although some formation of two or three consecutive IdoA-containing disaccharide units was observed
biosynthesis, capsular, polysaccharide, Escherichia, Escherichia coli, capsular polysaccharide, epimerase, mechanism, dermatan sulphate, fructose, reaction, substrate
Structure type: polymer chemical repeating unit
Location inside paper: abstract
Trivial name: chondroitin
Compound class: CPS
Contained glycoepitopes: IEDB_115136,IEDB_130648,IEDB_137473,IEDB_140630,IEDB_153510,IEDB_423153
Biosynthesis and genetic data: biosynthetic data
Comments, role: defructosylated polysaccharide
Related record ID(s): 5722, 6606, 6896, 6938, 8800, 9001, 9301, 10190
NCBI Taxonomy refs (TaxIDs): 562Reference(s) to other database(s): GTC:G43702JT, GlycomeDB:
2738
Show glycosyltransferases
There is only one chemically distinct structure:
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