Identification and Characterization of a Novel Cold-Adapted GH15 Family Trehalase from the Psychrotolerant Microbacterium phyllosphaerae LW106

Psychrophiles inhabiting various cold environments are regarded as having evolved diverse physiological and molecular strategies, such as the accumulation of trehalose to alleviate cold stress. To investigate the possible contributions of trehalose metabolism-related enzymes to cold-adaption in psychrotrophic bacteria and enrich the resource bank of trehalose hydrolysis enzymes, a novel cold-adapted GH15 GA-like trehalase (MpTre15A) from psychrotolerant Microbacterium phyllosphaerae LW106 isolated from glacier sediments was cloned and characterized. The recombinant MpTre15A from M. phyllosphaerae LW106 was expressed and purified in Escherichia coli BL21(DE3). The purified MpTre15A functioned as a hexamer and displayed maximal activity at pH 5.0 and 50 degrees C. Substrate specificity assay proved MpTre15A only showed hydrolytic activity toward alpha,alpha-trehalose. Site-directed mutation verified the key catalytic sites of G1u392 and G1u557 in MpTre15A. The k(cat) and k(cat) /K-m values of MpTre15A at 4 degrees C (104.50 s(-1) and 1.6 s(-1) mM(-1), respectively) were comparable to those observed for thermophilic GH15 trehalases at 50 degrees C, revealing its typical cold-adaptability. MpTre15A showed a trehalose conversion rate of 100% and 99.4% after 10 min and 15 min of incubation at 50 degrees C and 37 degrees C, respectively. In conclusion, this novel cold-adapted alpha,alpha-trehalase MpTre15A showed potential application for developing therapeutic enzymes, enzyme-based biosensors, and enzyme additives in the fermentation industry.