Hydrolysis of soybean isoflavonoid glycosides by Dalbergia beta-glucosidases.

Two beta-glucosidases from the legumes Dalbergia cochinchinensis and Dalbergia nigrescens were compared for their ability to hydrolyze isoflavonoid glycosides from soybean. Both D. nigrescens and D. cochinchinensis beta-glucosidases could hydrolyze conjugated soybean glycosides, but D. nigrescens beta-glucosidase hydrolyzed both conjugated and nonconjugated glycosides in crude soybean extract more rapidly. The kinetic properties Km, kcat, and kcat/Km of the Dalbergia beta-glucosidases toward conjugated isoflavonoid glycosides, determined using high-performance liquid chromatography, confirmed the higher efficiency of the D. nigrescens beta-glucosidase in hydrolyzing these substrates. The D. nigrescens beta-glucosidase could also efficiently hydrolyze isoflavone glycosides in soy flour suspensions, suggesting its application to increase free isoflavones in soy products.