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

摘要

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 β-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 β-glucosidase and is difficult to achieve synthetically.