Isolation of membranes containing protease from the cotyledons of germinating pea seeds

Membranes containing protease were isolated from the cotyledonsof germinating pea seeds by differential and two successivesucrose density gradient centrifugations. Membranes were recoveredin the microsomal fraction, but could be clearly separated frommembranes carrying antimycin A-insensitive NADH-cytochrome creductase EC 1.6.2.1 EC] ), which seem to come from the endoplasmicreticulum. The density of protease-containing membranes was1.135. Membranes contained a lower amount of phospholipid ascompared with the endoplasmic reticulum. Electron microscopicobservations also showed that the membranes were different fromthe smooth-surfaced endoplasmic reticulum. ¹Present address: Department of Pathology, Aichi Medical University,Nagakute, Aichi, Japan. (Received September 12, 1973; )