Purification of cytosolic beta-glucosidase from pig liver and its reactivity towards flavonoid glycosides

Biochim Biophys Acta. 1999 Nov 16;1435(1-2):110-6. doi: 10.1016/s0167-4838(99)00213-7.

Abstract

Flavonoid glycosides are common dietary components which may have health-promoting activities. The metabolism of these compounds is thought to influence their bioactivity and uptake from the small intestine. It has been suggested that the enzyme cytosolic beta-glucosidase could deglycosylate certain flavonoid glycosides. To test this hypothesis, the enzyme was purified to homogeneity from pig liver for the first time. It was found to have a molecular weight (55 kDa) and specific activity (with p-nitrophenol glucoside) consistent with other mammalian cytosolic beta-glucosidases. The pure enzyme was indeed found to deglycosylate various flavonoid glycosides. Genistein 7-glucoside, daidzein 7-glucoside, apigenin 7-glucoside and naringenin 7-glucoside all acted as substrates, but we were unable to detect activity with naringenin 7-rhamnoglucoside. Quercetin 4'-glucoside was a substrate, but neither quercetin 3, 4'-diglucoside, quercetin 3-glucoside nor quercetin 3-rhamnoglucoside were deglycosylated. Estimates of K(m) ranged from 25 to 90 microM while those for V(max) were about 10% of that found with the standard artificial substrate p-nitrophenol glucoside. The non-substrate quercetin 3-glucoside was found to partially inhibit deglycosylation of quercetin 4'-glucoside, but it had no effect upon activity with p-nitrophenol glucoside. This study confirms that mammalian cytosolic beta-glucosidase can deglycosylate some, but not all, common dietary flavonoid glycosides. This enzyme may, therefore, be important in the metabolism of these compounds.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cytosol / enzymology
  • Flavonoids / chemistry
  • Glycosides / chemistry
  • Hydrolysis
  • Kinetics
  • Liver / enzymology*
  • Swine
  • beta-Glucosidase / antagonists & inhibitors
  • beta-Glucosidase / chemistry
  • beta-Glucosidase / isolation & purification*

Substances

  • Flavonoids
  • Glycosides
  • beta-Glucosidase