Species: Glycine max
Molecular Weight of Polypeptide: 165 kD (experimental) [Hsieh01 ]
Enzymatic reaction of: isoflavone-7-O-glucoside β-glucosidase
The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.
The reaction is favored in the direction shown.
In Pathways: biochanin A conjugates interconversion
The isoflavone-7-O-glucoside hydrolysis catalyses the last step in the interconversion of isoflavone conjugates. The release of the aglycons daidzein, genistein, biochanin a and formononetin, facilitates the recurrence of those compounds in the biosynthetic route towards phytoalexins as immediate defense response or as substrates that may re-enter the cycle to replenish the isoflavone conjugate pool.
The dimeric (80 and 75 kD subunits) isoflavone-7-O-glucoside β-glucosidase exhibits a pronounced specificity towards glucose [Hsieh01] attached to the 7-O position of the flavonoid nucleus (biochanin A, formononetin, daidzein, genistein).
Other compounds than isoflavones are much poorer substrates and isoflavones or flavonole being glucosylated at the 3'- or 4'-O-position of the B-ring are not hydrolized at all [Hosel75]. It has been shown, that the 7-O-isoflavone specific β-glucosidase of Cicer arietinum was able to hydrolyze both the glucosyl and malonyl glucosyl isoflavones directly with similar kinetics [Hsieh01].
This may reflect the different biochemistry of the interconversion cycle in Glycine max compared to Cicer arietinum, since no esterase activity for malonyl glucosides of daidzein and genistein could be detected in soybean [Hosel75].
However, the existence of such a curtailed isoflavone conjugate cycle remains to be demonstrated.
T(opt): 30 °C [Hsieh01]
pH(opt): 6.0 [Hsieh01]
Hsieh01: Hsieh MC, Graham TL (2001). "Partial purification and characterization of a soybean β-glucosidase with high specific activity towards isoflavone conjugates." Phytochemistry 58(7);995-1005. PMID: 11730862
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