Biosynthesis of the Escherichia coli K4 capsule polysaccharide: a parallel system for studies of glycosyltransferases in chondroitin formation.
1997 (English)In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 272, no 5, 2682-2687 p.Article in journal (Refereed) Published
Escherichia coli K4 bacteria synthesize a capsule polysaccharide (GalNAc-GlcA(fructose))(n) with the carbohydrate backbone identical to chondroitin. GlcA- and GalNAc-transferase activities from the bacterial mem brane were assayed with accepters derived from the capsule polysaccharide and radiolabeled UDP-[C-14]GlcA and UDP-[H-3]GalNAc, respectively. It was shown that defructosylated oligosaccharides (chondroitin) could serve as substrates for both the GlcA- and the GalNAc-transferases. The radiolabeled products were completely degraded with chondroitinase AC; the [C-14]GlcA unit could be removed by beta-D-glucuronidase, and the [H-3]GalNAc could be removed by beta-N-acetylhexosaminidase. A fructosylated oligosaccharide acceptor tested for GlcA-transferase activity was found to be inactive. These results indicate that the chain elongation reaction of the K4 polysaccharide proceeds in the same way as the polymerization of the chondroitin chain, by the addition of the monosaccharide units one by one to the nonreducing end of the polymer. This makes the biosynthesis of the K4 polysaccharide an interesting parallel system for studies of chondroitin sulfate biosynthesis. In the biosynthesis of capsule polysaccharides from E. coli, a similar mechanism has earlier been demonstrated for polysialic acid (NeuNAc)(n) (Rohr, T. E., and Troy, F. A. (1980) J. Biol. Chem. 255, 2332-2342) and for the K5 polysaccharide (GlcA beta 1-4GlcNAc alpha 1-4)(n) (Lidholt, K., Fjelstad, M., Jann, K., and Lindahl, U. (1994) Carbohydr. Res. 255, 87-101). In contrast, chain elongation of hyaluronan (GlcA beta 1-3GlcNAc beta 1-4)(n) is claimed to occur at the reducing end (Prehm, P. (1983) Biochem. J. 211, 181-189).
Place, publisher, year, edition, pages
1997. Vol. 272, no 5, 2682-2687 p.
IdentifiersURN: urn:nbn:se:uu:diva-52353ISI: A1997WE66700017PubMedID: 9006904OAI: oai:DiVA.org:uu-52353DiVA: diva2:80262