Expression of Streptomyces coelicolor α-Galactosidase Gene in Escherichia coli and Characterization

Abstract

An α-galactosidase gene belonging to glycoside hydrolase family 27 from Streptomyces coelicolor was cloned and expressed in E. coli. The purified enzyme showed a single protein band on SDS-PAGE with a molecular mass of 64kDa. It was quite stable from pH 5.0 to 10.0 after treatment at 40°C for 60min, and was thermally stable up to 50°C. The enzyme acted on galacto-oligosaccharides, galactomanno-oligosaccharides and galactomannans as well as plant α-galactosidases. It consisted of an N-terminal catalytic domain (400 amino acid residues) and a C-terminal region (260 amino acid residues). The catalytic domain of the enzyme was constructed by deleting the C-terminal region from the enzyme and was found to be stable from pH 5.5 to 8.5 and up to 40°C. The catalytic domain showed the same specificity towards galacto-oligosaccharides, galactomanno-oligosaccharides and galactomannans as the enzyme containing the C-terminal region. These results indicated that the Cterminal region probably has an important role in stabilizing the enzyme.