Dietary flavonoid and isoflavone glycosides are hydrolysed by the lactase site of lactase phlorizin hydrolase

Lactase phlorizin hydrolase (LPH; EC 3.2.1.62) is a membrane-bound, family 1 beta-glycosidase found on the brush border of the mammalian small intesti ne, LPH purified from sheep small intestine, was capable of hydrolysing a r ange of flavonol and isoflavone glycosides. The catalytic efficiency (k(cat )/ K-m) for the hydrolysis of quercetin-4'-glucoside, quercetin-3-glucoside , genistein-7-glucoside and daidzein-7-glucoside was 170, 137, 77 and 1 1 ( mM(-1) s(-1)) respectively, The majority of the activity occurred at the la ctase and not phlorizin hydrolase site. The ability of LPH to deglycosylate dietary (iso)flavonoid glycosides suggests a possible role for this enzyme in the metabolism of these biologically active compounds. (C) 2000 Federat ion of European Biochemical Societies.