UDP-Glucuronic Acid Decarboxylases of Bacteroides fragilis and Their Prevalence in Bacteria

Abstract

Xylose is rarely described as a component of bacterial glycans. UDP-xylose is the nucleotide-activated form necessary for incorporation of xylose into glycans and is synthesized by the decarboxylation of UDP-glucuronic acid (UDP-GlcA). Enzymes with UDP-GlcA decarboxylase activity include those that lead to the formation of UDP-xylose as the end product (Uxs type) and those synthesizing UDP-xylose as an intermediate (ArnA and RsU4kpxs types). In this report, we identify and confirm the activities of two Uxs-type UDP-GlcA decarboxylases of Bacteroides fragilis, designated BfUxs1 and BfUxs2. Bfuxs1 is located in a conserved region of the B. fragilis genome, whereas Bfuxs2 is in the heterogeneous capsular polysaccharide F (PSF) biosynthesis locus. Deletion of either gene separately does not result in the loss of a detectable phenotype, but deletion of both genes abrogates PSF synthesis, strongly suggesting that they are functional paralogs and that the B. fragilis NCTC 9343 PSF repeat unit contains xylose. UDP-GlcA decarboxylases are often annotated incorrectly as NAD-dependent epimerases/dehydratases; therefore, their prevalence in bacteria is underappreciated. Using available structural and mutational data, we devised a sequence pattern to detect bacterial genes encoding UDP-GlcA decarboxylase activity. We identified 826 predicted UDP-GlcA decarboxylase enzymes in diverse bacterial species, with the ArnA and RsU4kpxs types confined largely to proteobacterial species. These data suggest that xylose, or a monosaccharide requiring a UDP-xylose intermediate, is more prevalent in bacterial glycans than previously appreciated. Genes encoding BfUxs1-like enzymes are highly conserved in Bacteroides species, indicating that these abundant intestinal microbes may synthesize a conserved xylose-containing glycan.

Phylum‐wide general protein O‐glycosylation system of the Bacteroidetes

“…Correct clones were introduced into B. fragilis NCTC 9343 by conjugal transfer from E. coli . Selection for co‐integrate strains and recovery of deletants was performed as previously described (Coyne et al ., ).…”

Antisense expression of Gossypium hirsutum UDP-glucuronate decarboxylase in Arabidopsis leads to changes in cell wall components

“…Therefore, UXS has a crucial role for the conversion of diverse polysaccharides in the cell walls of plant, fungal, and bacterial glycans, and glycosaminoglycans in higher organisms (Reisset al, 1985;York and O'Neill, 2008;Coyne et al, 2011;Eixelsberger et al, 2012). At least three GhUXS genes are involved in the biosynthesis of fiber cell walls in cotton.…”

“…Its activity has now been reported in other microorganisms, vertebrate species, and plants. From various species of bacteria, 826 predicted UXS enzymes have been identified, suggesting that xylose is more prevalent in bacterial glycans (Coyne et al, 2011). In zebrafish, UXS1 activity is essential for functional deposition of proteoglycans in the extracellular matrix (Eames et al, 2010).…”

Saturation transfer difference NMR to study substrate and product binding to human UDP-xylose synthase (hUXS1A) during catalytic event

“…3 UDP-GlcUA is also involved in O-glucuronidation of small molecules in xenobiotic metabolism. 4,9 It is, however, generated by various alternative routes in different species. Varying metabolic pathways depend on different enzymatic catalysis as shown in Scheme 1.…”

“…2 Further, it acts as substrate in the formation of several carbohydrates in different organisms. [4][5][6][7][8][9] different tissues, which may lead to e.g. [4][5][6][7][8] The currently most intensively studied pathway is the mammalian UDP-xylose synthase (UXS) catalyzed formation of UDP-xylose (UDP-Xyl).…”