Molecular cloning and biochemical characterization of a trehalose synthase from Myxococcus sp. strain V11.

The tresI gene of Myxococcus sp. strain V11 was cloned, and found to encode a trehalose synthase comprising 551 amino acids. The deduced molecular weight of the encoded TreS I protein 64.7 kDa and the isoelectric point (pI) was predicted to be 5.6. The catalytic cleft consists of the Asp202-Glu244-Asp310 catalytic triad and additional conserved residues. The recombinant (His)6-tag enzyme was expressed in Escherichia coli BL21(DE3) and purified by Ni2+-affinity chromatography, resulting in a specific activity of up to 172.7 U/mg. TLC and HPLC results confirmed that rTreS I can convert maltose into trehalose, with a yield of 61%. The KM and Vmax values of recombinant TreS I for maltose were 0.62 mM and 25.5 mM min-1 mg-1 protein, respectively. TreS I was optimally active at 35° and stable at temperatures of <25 °C. TreS I was stable within a narrow range of pH values, from 6.0 to 7.0. The enzymatic activity was slightly stimulated by Mg2+ and strongly inhibited by Fe3+, Co2+ and Cu2+. TreS I was also strongly inhibited by SDS and weakly by EDTA and TritonX-100.