BioChem - DOS

Biosynthesis of Cytidine Diphosphate-6-d-Glucitol for the Capsular Polysaccharides of Campylobacter jejuni

Biochemistry

Ghosh, Manas K.; Narindoshvili, Tamari; Thoden, James B.; Schumann, Mitchell E.; Holden, Hazel M.; Raushel, Frank M.

<P><I>Campylobacter jejuni</I> is a Gram-negative pathogenic bacterium commonly found in chickens and is the leading cause of human diarrheal disease worldwide. The various serotypes of <I>C. jejuni</I> produce structurally distinct capsular polysaccharides (CPSs) on the exterior surfaces of the cell wall. The capsular polysaccharide from <I>C. jejuni</I> serotype HS:5 is composed of a repeating sequence of <SMALL>D</SMALL>-<I>glycero</I>-<SMALL>D</SMALL>-<I>manno</I>-heptose and <SMALL>D</SMALL>-glucitol-6-phosphate. We previously defined the pathway for the production of <SMALL>D</SMALL>-<I>glycero</I>-<SMALL>D</SMALL>-<I>manno</I>-heptose in <I>C. jejuni</I>. Here, we elucidate the biosynthetic pathway for the assembly of cytidine diphosphate (CDP)-6-<SMALL>D</SMALL>-glucitol by the combined action of two previously uncharacterized enzymes. The first enzyme catalyzes the formation of CDP-6-<SMALL>D</SMALL>-fructose from cytidine triphosphate (CTP) and <SMALL>D</SMALL>-fructose-6-phosphate. The second enzyme reduces CDP-6-<SMALL>D</SMALL>-fructose with NADPH to generate CDP-6-<SMALL>D</SMALL>-glucitol. Using sequence similarity network (SSN) and genome neighborhood network (GNN) analyses, we predict that these pairs of proteins are responsible for the biosynthesis of CDP-6-<SMALL>D</SMALL>-glucitol and/or CDP-<SMALL>D</SMALL>-mannitol in the lipopolysaccharides (LPSs) and capsular polysaccharides in more than 200 other organisms. In addition, high resolution X-ray structures of the second enzyme are reported, which provide novel insight into the manner in which an open-chain nucleotide-linked sugar is harbored in an active site cleft.</P><BR>[FIG OMISSION]</BR>

2024

American Chemical Society

0006-2960

1520-4995

63

5

pp.699-710

10.1021/acs.biochem.3c00706

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