PARTIAL-PURIFICATION AND CHARACTERIZATION OF VARIOUS BETA-GLUCOSIDASES ASSOCIATED WITH CELLULAR-COMPONENTS OF CORN ROOTS

Beta-Glucosidases were isolated from various cellular components from corn root cortical tissue. The subcellular components were separated and the enzymes were partially purified and characterized, The pH-activity profile of the cytosolic enzyme and the unidentified particulate-associated beta-glucosidase were identical. Further kinetic analyses of these two enzymes at pH 5.5 and 7.5 suggests that the unidentified particulate-associated beta-glucosidase is the bound form of the cytosolic enzyme. The ionically bound cell wall enzyme (in muro) had a pH optimum of 5.5 while the free form (salt solubilized) had a pH optimum of 5.0. The enzyme kinetics of the extracellular enzymes were compared to the intracellular forms with particular reference to bound versus free enzymes. The K(m) values and the shape of the kinetic curves of free enzymes were not changed when enzymes were assayed in the bound state. The tightly bound cell wall enzyme had a very broad pH-activity profile and had K(m) value approximately one-half the K(m) value of the other beta-glucosidases.