Beta-glucosidase activity in corn roots. Problems in subcellular fractionation

Preliminary results from differential centrifugation experiments, washing treatments, and enrichment in linear sucrose gradients at a density of 1.09 grams per cubic centimeter all indicated that β-glucosidase activity in corn root homogenates was associated with a membrane such as tonoplast. A subsequent sucrose density gradient centrifugation time course showed that the β-glucosidase was actually a soluble enzyme which moved into the gradients. The problem of soluble enzymes contaminating light density membranes in sucrose gradients and the question of centrifugation time necessary for membrane vesicles to reach isopycnic conditions are addressed.