UNIQUE PROPERTIES OF CELL WALL-ASSOCIATED BETA-GLUCOSIDASES

Two maize (Zea mays L.) root cell wall-associated beta-glucosidases were compared to two cellular forms. The ionically bound cell wall enzyme was more difficult to dissociate from the cell wall compared to artifactually bound cytosolic beta-glucosidase activity. The ionically bound cell wall enzyme also had an isoelectric pH of 6.8-7.0 compared to the acid pI of the cytosolic enzyme (4.8-5.2). A second cell wall enzyme was very tightly bound to the cell wall and could not be extracted with 3 M NaCl or LiCl. Both the ionically bound cell wall beta-glucosidase and the tightly bound beta-glucosidase were more thermostable at 40-degrees-C and 50-degrees-C compared to the cytosolic enzyme and the particulate intracellular isozyme. The tightly bound cell wall beta-glucosidase was the only thermostable enzyme at 60-degrees-C.