Structural insights into the substrate specificity and activity of a novel mannose 2-epimerase from Runella slithyformis.

Mannose 2-epimerase (ME), a member of the acylglucosamine 2-epimerase (AGE) superfamily that catalyzes epimerization of D-mannose and D-glucose, has recently been characterized to have potential for D-mannose production. However, the substrate-recognition and catalytic mechanism of ME remains unknown. In this study, structures of Runella slithyformis ME (RsME) and its D254A mutant [RsME(D254A)] were determined in their apo forms and as intermediate-analog complexes [RsME-D-glucitol and RsME(D254A)-D-glucitol].

Enzymatic characteristics of D-mannose 2-epimerase, a new member of the acylglucosamine 2-epimerase superfamily.

Carbohydrate epimerases and isomerases are essential for the metabolism and synthesis of carbohydrates. In this study, Runella slithyformis Runsl_4512 and Dyadobacter fermentans Dfer_5652 were characterized from a cluster of uncharacterized proteins of the acylglucosamine 2-epimerase (AGE) superfamily. These proteins catalyzed the intramolecular conversion of D-mannose to D-glucose, whereas they did not act on β-(1 → 4)-mannobiose, N-acetyl-D-glucosamine, and D-fructose, which are substrates of known AGE superfamily members.