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

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          Abstract

          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 intestine. LPH, purified from sheep small intestine, was capable of hydrolysing a range 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 14 (mM(-1) s(-1)) respectively. The majority of the activity occurred at the lactase 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.

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          Most cited references18

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          The Flavonoids. A Class of Semi-Essential Food Components: Their Role in Human Nutrition

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            Relative bioavailability of the antioxidant flavonoid quercetin from various foods in man.

            Quercetin is a strong antioxidant and a major dietary flavonoid. Epidemiological studies suggest that consumption of quercetin protects against cardiovascular disease, but its absorption in man is controversial. We fed nine subjects a single large dose of onions, which contain glucose conjugates of quercetin, apples, which contain both glucose and non-glucose quercetin glycosides, or pure quercetin-3-rutinoside, the major quercetin glycoside in tea. Plasma levels were then measured over 36 h. Bioavailability of quercetin from apples and of pure quercetin rutinoside was both 30% relative to onions. Peak levels were achieved less than 0.7 h after ingestion of onions, 2.5 h after apples and 9 h after the rutinoside. Half-lives of elimination were 28 h for onions and 23 h for apples. We conclude that conjugation with glucose enhances absorption from the small gut. Because of the long half-lives of elimination, repeated consumption of quercetin-containing foods will cause accumulation of quercetin in blood.
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              Statistical estimations in enzyme kinetics.

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                Author and article information

                Journal
                FEBS Letters
                Elsevier BV
                00145793
                February 25 2000
                February 25 2000
                February 22 2000
                : 468
                : 2-3
                : 166-170
                Article
                10.1016/S0014-5793(00)01211-4
                10692580
                3b7575d6-ee36-47e0-9d23-8c1c24d78238
                © 2000

                http://doi.wiley.com/10.1002/tdm_license_1.1

                http://onlinelibrary.wiley.com/termsAndConditions#vor

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