N-Acetylmannosamine-6-phosphate 2-epimerase uses a novel substrate-assisted mechanism to catalyze amino sugar epimerization.

Abstract

There are five known general catalytic mechanisms used by enzymes to catalyze carbohydrate epimerization. The amino sugar epimerase N-acetylmannosamine-6-phosphate 2-epimerase (NanE) has been proposed to use a deprotonation-reprotonation mechanism, with an essential catalytic lysine required for both steps. However, the structural determinants of this mechanism are not clearly established. We characterized NanE from Staphylococcus aureus (SaNanE) using a new coupled assay to monitor NanE catalysis in real time, and found that it has kinetic constants comparable with other species. The crystal structure of SaNanE, which comprises a triosephosphate isomerase (TIM) barrel fold with an unusual d..