Crystal structure of trehalose synthase from Deinococcus radiodurans reveals an active conformation (LB142)

Abstract

Trehalose, a non‐reducing disaccharide, displays exceptional stability and has been used in the food, cosmetic, medical and biotechnological industries. Trehalose synthase catalyzes a simple conversion of maltose into trehalose and hence has great potential in industrial application. However, the disadvantages of low thermo‐stability and the side product of glucose by the hydrolytic activity are needed to be improved. TS belongs to the glycoside hydrolase family 13 (GH13), which represents the largest family of glycoside hydrolases, transferases and isomerases. Here we have determined a crystal structure of TS from Deinococcus radiodurans (DrTS), which consists of a catalytic (β/α)8 barrel, a subdomain B, a C‐terminal β domain and two TS‐unique subdomains (S7 and S8). The C‐terminal domain and S8 contribute the majority of the dimeric interface. The active‐site architecture of DrTS is virtually identical to those of several glycoside hydrolase 13 members, suggesting of an active conformation. However, the recently published TS structures from Mycobacterium smegmatis and M. tuberculosis display an inactive conformation because the S7 loop blocks the substrate‐binding site. A detailed comparison revealed open/closed conformations with distinct S7 structures and different inter‐domain orientations. Such conformational changes through subdomains during enzyme catalysis are also observed in other GH13 members. Based on the structural comparison, particularly with sucrose isomerase and sucrose hydrolase, several mutants are generated and characterized. Hopefully, the residues involved in isomerase/hydrolase activities will be identified.