Misincorporation of Galactose by Chondroitin Synthase of Escherichia coli K4: From Traces to Synthesis of Chondbiuronan, a Novel Chondroitin-Like Polysaccharide

14 December 2020
Nous venons de publier dans le journal BioMolecules une étude portant sur la synthèse de chondroïtine bactérienne dans une souche d’Escherichia coli recombinante. Cette étude met en avant le fait qu’en absence d’UDP-GalNAc qui est l’un des précurseurs de biosynthèse de la chondroïtine synthase KfoC, l’enzyme incorpore le galactose pour former le chondbiuronane, nouveau polysaccharide analogue structural de la chondroïtine. Cliquez sur le titre pour plus d'information.

Résumé:
« Chondroitin synthase KfoC is a bifunctional enzyme which polymerizes the capsular chondroitin backbone of Escherichia coli K4, composed of repeated β3N-acetylgalactosamine (GalNAc)-β4-glucuronic acid (GlcA) units. Sugar donors UDP-GalNAc and UDP-GlcA are the natural precursors of bacterial chondroitin synthesis. We have expressed KfoC in a recombinant strain of Escherichia coli deprived of 4-epimerase activity, thus incapable of supplying UDP-GalNAc in the bacterial cytoplasm. The strain was also co-expressing mammal galactose β-glucuronyltransferase, providing glucuronyl-lactose from exogenously added lactose, serving as a primer of polymerization. We show by the mean of NMR analyses that in those conditions, KfoC incorporates galactose, forming a chondroitin-like polymer composed of the repeated β3-galactose (Gal)-β4-glucuronic acid units. We also show that when UDP-GlcNAc 4-epimerase KfoA, encoded by the K4-operon, was co-expressed and produced UDP-GalNAc, a small proportion of galactose was still incorporated into the growing chain of chondroitin.  »

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