Clone, Expression and Characterization of the Thermostable ?-Galactosidase from Soil Metagenomic DNA of Taishan Mountain / 微生物学通报

A possible ?-Galactosidase gene(pwtsA) was discovered from soil metagenomic DNA of Taishan Mountain.PwtsA gene was inserted into the expression vector pET30a and transferred into E.coli BL21(DE3).Recombinant protein PWTSA was expressed as a soluble form at high level through IPTG induction,with a molecular mass of 57 kD analyzed by SDS-PAGE.PWTSA can produce o-nitrophenol from o-nitrophenol-?-D-galactopyranoside(ONPG),and its specific activity was determined as 13.6 U/mg.The enzymatic studies demonstrated that the recombinant protein PWTSA was a thermostable ?-Galactosidase,its optimum temperature and pH were 85?C～95?C and 6.5 respectively.In standard assays,the Km for ONPG was 0.83 mmol/L.