title: Hydrolysis of a naturally occurring beta-glucoside by a broad-specificity beta-glucosidase from liver.
abstract: We have isolated from guinea-pig liver a broad-specificity beta-glucosidase of unknown function that utilizes as its substrate non-physiological aryl glycosides (e.g. 4-methylumbelliferyl beta-D-glucopyranoside, p-nitrophenyl beta-D-glucopyranoside). The present paper documents that this enzyme can be inhibited by various naturally occurring glycosides, including L-picein, dhurrin and glucocheirolin. In addition, L-picein, which acts as a competitive inhibitor of the broad-specificity beta-glucosidase (Ki 0.65 mM), is also a substrate for this enzyme (Km 0.63 mM; Vmax. 277,000 units/mg). Heat-denaturation, kinetic competition studies, chromatographic properties and pH optima all argue strongly that the broad-specificity beta-glucosidase is responsible for the hydrolysis of both the non-physiological aryl glycosides and L-picein. This paper demonstrates that beta-glucosidase can catalyse the hydrolysis of a natural glycoside, and may provide a key to understanding the function of this enigmatic enzyme. A possible role in the metabolism of xenobiotic compounds is discussed.
mesh_terms: D000818:Animals; D005959:Glucosidases / Q000378:metabolism*; D005960:Glucosides / Q000378:metabolism*; D006027:Glycosides / Q000378:metabolism* / Q000494:pharmacology; D006168:Guinea Pigs; D006868:Hydrolysis; D006923:Hymecromone / Q000031:analogs & derivatives / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D009570:Nitriles / Q000494:pharmacology; D011489:Protein Denaturation; D013379:Substrate Specificity; D001617:beta-Glucosidase / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D005960:Glucosides; D006027:Glycosides; D009570:Nitriles; C014110:4-methylumbelliferyl glucoside; C050880:picein; D006923:Hymecromone; D005959:Glucosidases; D001617:beta-Glucosidase; C011220:dhurrin