• Journal of Microbiology and Biotechnology
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• 제10권5호
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• pp.638-642
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• 2000

A ${\beta}-glycosidase$ enzyme with $\beta$-D-fucosidase, ${\beta}-D-galactosidase$, and $\beta$-D-glucosidase activities has been purified from Thermus caldophilus GK24. The enzyme was monomeric with a molecular mass of 49 kDa, as evidenced by SDS-PAGE. The $K_m$ values for p-nitrophenyl ${\beta}-D-fucopyranoside$ (p-NPFuc), p-nitrophenyl ${\beta}-D-galactopyranoside$ (p-NPGal), and p-nitrophenyl ${\beta}-D-glucopyranoside$ (p-NPGlu) were 0.23 mM, 6.25 mM, and 0.28 mM, respectively. The enzyme showed optimal pH ranging between 5.5-6.5 and maximum temperature in the range of $85-90^{\circ}C$ for all the above mentioned activities. The half-life of the enzyme in sodium phosphate buffer (pH 6.0) at $80^{\circ}C$ was approximately 7 h. The p-NPGal hydrolyzing activity of Tca ${\beta}-glycosidase$ was strongly activated by L-histidine, while the p-NPFuc and p-NPGlu hydrolyzing activities of Tca ${\beta}-glycosidase$ were not affected at all by the amino acid. These results suggest differences in the conformation or in the reactive residues at the active site of Tca ${\beta}-glycosidase$.