Partial purification and characterization of various β-glucosidases associated with cellular components of corn roots

Abstract β-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 β-glucosidase were identical. Further kinetic analyses of these two enzymes at pH 5.5 and 7.5 suggests that the unidentified particulate-associated β-glucosidase is the bound from of the cytosolic enzyme. The ionically bound cell wall enzyme (in muro) had a pH optimum of 5.5 while the free from (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 a K m value approximately one-half the K m value of the other β-glucosidases.