Aldose 1-epimerase, similar to Escherichia coli YihR
Proteins similar to Escherichia coli YihR are uncharacterized members of 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.
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