Abstract: 【Objective】 Trehalose synthase（EC. 5. 4. 99. 16）, which converts maltose to trehalose,is considered to be a potential biocatalyst for trehalose production. This enzymatic process has the advantage of a simple reaction and uses an inexpensive substrate. We aimed to discover and characterize a trehalose synthase from Myxococcus sp. CYD-1.【Method】 Genomic DNA extracted from strain CYD-1 was used as a template for trehalose synthase gene cloning by PCR reaction. The PCR product was digested with restriction endonucleases Nde I and Hind Ⅲ and then ligated into pET-29a vector. After plasmid transformation into E. coli BL21（DE3） cells,the recombinant enzyme was expressed by IPTG induction and purified by nickel affinity chromatography(Ni²⁺-NTA). Characterization of recombinant rMCTs,including optimal pH and temperature,metal ion dependence,and inhibitor,was performed using maltose as the substrate. The effect of pH and temperature on the enzyme activity was also measured.【Result】 A trehalose synthase gene（MCTs） isolated from Myxococcus sp. CYD-1,encoding 552 amino acids with a putative molecular size of 65 kU,was expressed and characterized. The amino acid sequence of MCTs shared the highest identity（92. 36%） with the trehalose synthase from Myxococcus sp. V11,but it is completely different from other experimentally characterized bacterial trehalose synthases. The results of homology modeling showed that MCTs possess the common trehalose synthase motifs such as ²⁰²DAVPYL²⁰⁷,²⁴⁴EANQ²⁴⁷ and ³⁰⁷RNHDEL³¹². A catalytic triad Asp202-Glu244-Asp330 was shown to be conserved in the MCTs. Threedimensional modeling results show that MCTs has a typical（α/β）₈-barrel structure,indicating that MCTs belongs to the glycosyl hydrolase family 13. The purified recombinant enzyme had an optimum temperature of 40 ℃ and a pH optimum around 6. 5. For the target substrate maltose,the specific enzyme activity of rMCTs was calculated to be approximately 105. 6 U/mg protein under the optimal reaction conditions. The rMCTs retained full activity after 4 h of incubation at below 30°C and retained about 50%,but it lost 100%of the original activity after 1. 5 h of incubation at 65 ℃. In terms of pH,the rMCTs was active in a narrow range of pH（5. 0～8. 0） conditions,and the enzyme was stable in the range of pH 6. 0～7. 5 in treatments at 4 ℃ for 12 h. The enzyme activity was slightly stimulated by Ca²⁺,and strongly inhibited by 1 mmol/L Co²⁺,Fe³⁺,Cu²⁺. Other metal ions had almost no effect. Recombinant enzyme activity was strongly inhibited by 5 mg/mL SDS,10% acetone,ethanol and acetonitrile and weakly inhibited by 20 mg/mL TritonX-100.【Conclusion】 The results of the characterization showed that it could be a potential novel enzyme in industrial applications.