X-ray structure of Arthrobacter globiformis M30 ketose 3-epimerase for the production of d-allulose from d-fructose

Abstract

The crystal structure of A. globiformis M30 ketose 3-epimerase was determined at 1.96 Å resolution.

Abstract

The X-ray structure of ketose 3-epimerase from Arthrobacter globiformis M30, which was previously reported to be a d-allulose 3-epimerase (AgD-AE), was determined at 1.96 Å resolution. The crystal belonged to the hexagonal space group P6 ₅22, with unit-cell parameters a = b = 103.98, c = 256.53 Å. The structure was solved by molecular replacement using the structure of Mesorhizobium loti l-ribulose 3-epimerase (MlL-RE), which has 41% sequence identity, as a search model. A hexagonal crystal contained two molecules in the asymmetric unit, and AgD-AE formed a homotetramer with twofold symmetry. The overall structure of AgD-AE was more similar to that of MlL-RE than to the known structures of d-psicose (alternative name d-allulose) 3-epimerases ( d-PEs or d-AEs), although AgD-AE and MlL-RE have different substrate specificities. Both AgD-AE and MlL-RE have long helices in the C-terminal region that would contribute to the stability of the homotetramer. AgD-AE showed higher enzymatic activity for l-ribulose than d-allulose; however, AgD-AE is stable and is a unique useful enzyme for the production of d-allulose from d-fructose.