Salmonella enterica serovar Typhi DeoM (earlier named as DeoX) is a mutarotase with high specificity for deoxyribose. It is encoded by one of four genes beonging to the deoK operon. This operon has also been found in Escherichia coli where it is more common in pathogenic than in commensal strains and is associated with pathogenicity. It has been found on a pathogenicity island from a human blood isolate AL863 and confers the ability to use deoxyribose as a carbon source; deoxyribose is not fermented by non-pathogenic E.coli K-12. Proteins in this family are members of the aldose-1-epimerase superfamily. Aldose 1-epimerases, or mutarotases, are key enzymes of carbohydrate metabolism, catalyzing the interconversion of the alpha- and beta-anomers of hexose sugars such as glucose and galactose. This interconversion is an important step that allows anomer specific metabolic conversion of sugars. Studies of the catalytic mechanism of the best known member of the family, galactose mutarotase, have shown a glutamate and a histidine residue to be critical for catalysis; the glutamate serves as the active site base to initiate the reaction by removing the proton from the C-1 hydroxyl group of the sugar substrate, and the histidine as the active site acid to protonate the C-5 ring oxygen. Site directed mutagenesis of this latter histidine residue renders Salmonella enterica DeoM inactive.
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