Crystal structure of l -rhamnose 1-dehydrogenase involved in the nonphosphorylative pathway of l -rhamnose metabolism in bacteria

[摘要] Several microorganisms can utilize l -rhamnose as a carbon and energy source through the nonphosphorylative metabolic pathway, in which l -rhamnose 1-dehydrogenase (RhaDH) catalyzes the NAD(P) + -dependent oxidization of l -rhamnose to l -rhamnono-1,4-lactone. We herein investigated the crystal structures of RhaDH from Azotobacter vinelandii in ligand-free, NAD + -bound, NADP + -bound, and l -rhamnose- and NAD + -bound forms at 1.9, 2.1, 2.4, and 1.6 Å resolution, respectively. The significant interactions with the 2′-phosphate group of NADP + , but not the 2′-hydroxyl group of NAD + , were consistent with a preference for NADP + over NAD + . The C5-OH and C6-methyl groups of l -rhamnose were recognized by specific residues of RhaDH through hydrogen bonds and hydrophobic contact, respectively, which contribute to the different substrate specificities from other aldose 1-dehydrogenases in the short-chain dehydrogenase/reductase superfamily.

[关键词] aldose 1-dehydrogenase;crystal structure;l-rhamnose metabolism;short-chain dehydrogenase/reductase