The enzyme is involved in synthesis of paratose and tyvelose, unusual 3,6-dideoxyhexose sugars that form part of the O-antigen in the lipopolysaccharides of several enteric bacteria. Isolated from Salmonella enterica subsp. enterica serovar Typhi (Salmonella typhi).
The expected taxonomic range for this enzyme is: Salmonella enterica subsp. enterica serovar Typhi
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SYSTEMATIC NAME
IUBMB Comments
CDP-alpha-D-paratose:NADP+ 4-oxidoreductase
The enzyme is involved in synthesis of paratose and tyvelose, unusual 3,6-dideoxyhexose sugars that form part of the O-antigen in the lipopolysaccharides of several enteric bacteria. Isolated from Salmonella enterica subsp. enterica serovar Typhi (Salmonella typhi).
Substrates: enzyme catalyzes the stereospecific hydride transfer of the pro-S hydrogen from the C-4' position of the reduced coenzyme to C-4 of the substrate, CDP-3,6-dideoxy-D-glycero-D-glycero-4-hexulose. The overall equilibrium of this catalysis greatly favors the formation of the reduced sugar product and the oxidized coenzyme Products: -
NADPH is 10fold prefered over NADH. Enzyme exhibits a high affinity for NADPH with a much smaller dissociation constant of 0.005microM compared to the Km of 0.26 mM
competitive inhibitor with respect to NADPH and either an uncompetitive or a mixed type inhibitor with respect to CDP-3,6-dideoxy-D-glycero-D-glycero-4-hexulose
competitive inhibitor with respect to CDP-3,6-dideoxy-D-glycero-D-glycero-4-hexulose and either an uncompetitive or a mixed type inhibitor with respect to NADPH
Salmonella serogroup polymorphism based on abequose and paratose arose by divergence from an ancestral gene to give abequose and paratose synthase in different strains or species, and this happened in a bacterial group with low G+C content. Later a recombination event brought either paratose synthase gene rfbS or abeqouse synthase gene rJbJ into the genetic background of the other. These events were followed by one form being picked up by a Salmonella strain and becoming adapted to put a dideoxyhexose into its own 0-antigen
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