Biosynthesis of the E.coli K4 capsule polysaccharide: a parallel system for studies of glycosyltransferases in chondroitin formation
1997 (English)In: The Journal of Biological Chemistry, ISSN 0021-9258, 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 carbohydratebackbone identical to chondroitin. GlcA- andGalNAc-transferase activities from the bacterial membranewere assayed with acceptors derived from thecapsule polysaccharide and radiolabeled UDP-[14C]GlcAand UDP-[3H]GalNAc, respectively. It was shown thatdefructosylated oligosaccharides (chondroitin) couldserve as substrates for both the GlcA- and the GalNActransferases.The radiolabeled products were completelydegraded with chondroitinase AC; the [14C]GlcAunit could be removed by b-D-glucuronidase, and the[3H]GalNAc could be removed by b-N-acetylhexosaminidase.A fructosylated oligosaccharide acceptor testedfor GlcA-transferase activity was found to be inactive.These results indicate that the chain elongation reactionof the K4 polysaccharide proceeds in the same wayas the polymerization of the chondroitin chain, by theaddition of the monosaccharide units one by one to thenonreducing end of the polymer. This makes the biosynthesisof the K4 polysaccharide an interesting parallelsystem for studies of chondroitin sulfate biosynthesis.In the biosynthesis of capsule polysaccharides from E.coli, a similar mechanism has earlier been demonstratedfor polysialic acid (NeuNAc)n (Rohr, T. E., and Troy, F. A.(1980) J. Biol. Chem. 255, 2332–2342) and for the K5 polysaccharide(GlcAb1–4GlcNAca1–4)n (Lidholt, K., Fjelstad,M., Jann, K., and Lindahl, U. (1994) Carbohydr. Res.255, 87–101). In contrast, chain elongation of hyaluronan(GlcAb1–3GlcNAcb1–4)n is claimed to occur at the reducingend (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-52693OAI: oai:DiVA.org:uu-52693DiVA: diva2:80603