Characterization of a β-Glucosidase Encoded by a Gene from Cellvibrio gilvus

抄録

An aryl-β-cellobioside-hydrolyzing enzyme was obtained from Escherichia coli WL66 infected with a recombinant phage, λCG23, harboring a 7.2-Kbp DNA fragment from Cellvibrio gilvus. It was purified by hydrophobic, ion exchange and gel filtration chromatographies to an electrophoretically homogeneous state. The purified enzyme has a molecular weight of 82, 000 and a pI of 6.0, and its amino terminal amino acid sequence was identified. It produced glucose from a series of cellooligosaccharides and aryl-β-glucosides such as 4-methylumbelliferyl-β-glucoside and pnitrophenyl-β-glucoside. Although the enzyme released 4-methyumbelliferon from 4-methylumbelliferyl-β-cellobioside, the rate of its release was much slower than the rate of glucose release. From these results the purified enzyme was identified as β-glucosidase (EC 3.2.1.21). However, its action on cellobiose was substantially lower than the action on higher cellooligosaccharides.