A β-glucosidase from Novosphingobium sp GX9 with high catalytic efficiency toward isoflavonoid glycoside hydrolysis and (+)-catechin transglycosylation

In view of the important role of isoflavonoids and their related glycoconjugates in human health, there is considerable interest in their enzymatic conversion. SBGL, a novel beta-glucosidase isolated from Novosphingobium sp. GX9, was expressed in Escherichia coli and found to have high activity for hydrolysis of daidzin and genistin. SBGL showed very low K (m) values for daidzin and genistin, and the k (cat)/K (m) values for these substrates were 33,300 and 19,200 s(-1) mM(-1), respectively. The SBGL glucosidase could also transglycosylate the flavanol (+)-catechin at saturating acceptor concentrations, which has not previously been reported for a beta-glucosidase and is difficult to achieve synthetically.