The pH dependent distribution of β-glucosidase activity in isolated particulate fractions

Abstract Higher levels of β-glucosidase activity were found in particulate fractions isolated from corn roots under alkaline compared to acid conditions. The greatest pH effect was observed on the crude cell wall fraction (1000× g for 10 min) where 19% of the total β-glucosidase activity was recovered at pH 7.7 compared to 3% at pH 6.0. Further analysis indicated that the particulate activity recovered in the 1000× g pellet was dissociated over a narrow range of pH. To determine if the pH effect was on the cell wall or a subcellular component found in the crude cell wall fraction, cell walls were separated from organelles and membranes by sucrose density gradient centrifugation. Most of the β-glucosidase activity in the crude cell wall fraction was not associated with the cell wall but with an unidentified component which equilibrated at 51% (w/w) sucrose.