Isolation and Characterization of an Enzyme with β-Glucosidase and β-Fucosidase Activities from Dalbergia cochinchinensis Pierre

抄録

A glycosidase enzyme with both β-glucosidase and β-fucosidase activities has been purified from the seeds of Dalbergia cochinchinensis Pierre (Thai Rosewood) by ammonium sulfate fractionation, preparative isoelectric focusing, and Sephadex G-150 chromatography. The enzyme has molecular weights of 330, 000 in the native state and 66, 000 in the denatured state. Hydrolysis of p-NP-β-D-glucoside and p-NP-β-D-fucoside showed pH optimum at pH 5.0 and was inhibited by δ-gluconolactone, HgCl₂, and p-chloromercuribenzoate. The K_m and k_cat values of the purified enzyme were 5.4mM and 307s^-1 for p-NP-β-D-glucoside and 0.54mM and 151s^-1 for p-NP-β-D-fucoside, so that the latter had by far the higher k_cat/K_m ratio. p-NP-β-D-galactoside, p-NP-β-D-xyloside, and p-NP-α-L-arabinoside were hydrolyzed more slowly. Hydrolysis of sophorose, laminaribiose, and gentiobiose were also rather slow, and hydrolysis of cellobiose was even slower. No hydrolysis of the cyanogenic glucosides linamarin or prunasin, but some hydrolysis of amygdalin and salicin was found. Further studies are required to identify the natural substrates of the enzyme. However, high yields, ease of purification, and storage stability of the enzyme make it a useful candidate for various applications, such as study of oligosaccharide synthesis by reversal of hydrolysis.