Association of Latent Cellulase Activity with Plasma Membranes from Kidney Bean Abscission Zones

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Abstract
Membranes isolated from abscission zones of Phaseolus vulgaris L., cv. Red Kidney, contained cellulase activity. This particulate activity was enhanced 10- to 20-fold by treatment with Triton X-100. Sucrose density gradient analyses of cell fractions showed that the membranes with which cellulase was associated had a peak equilibrium density of 1.16 to 1.17 g/cm3 which coincided with that of ion-activated ATPase, a marker for plasma membranes. The membrane fraction having the highest cellulase activity also contained a high proportion of plasma membranes as shown by electron microscopy of sucrose density gradient fractions after staining by periodic acid-chromic acid-phosphotungstic acid. It was concluded that the particulate cellulase was associated with the plasma membrane.