Glycosidases of Phaseolus vulgaris

The enzymes, cr-galactosidase, P-galactosidase, a-mannosidase, P-glucosidase, and p-acetylglucosaminidase, have been purified from the germinating seeds of Phaseolus vulgaris. All five enzymes have been simultaneously isolated in a highly active form. The pH optimum, K,,,, and energy of activation of each glycosidase for the reaction of hydrolysis of the appropriate P-nitrophenyl glycoside have been determined. The specificity of the enzymes has been studied by using synthetic and natural substrates such as melibiose, r&ose, stachyose, lactose, mannobiose, methyl cx-D-mannopyranoside, cellobiose, gentiobiose, sophorose, and methyl P-D-glucopyranoside. All these enzymes appear to be highly specific for the glycopyranosyl group and the anomeric configuration of the glycosidic linkage. Their action on macromolecules, such as galactomannans from guar and locust bean gums, desialyzed fetuin and its tryptic glycopeptides, a glycopeptide from orosomucoid, and ribonuclease B, has been studied.