Isolation of protein bodies on sucrose gradients

Summary Storage protein bodies from sunflower cotyledons during early stages of seed germination were isolated on sucrose density gradients by isopycnic centrifugation. The density of this organelle on the gradients ranged between 1.26 and 1.36 g cm^-3. A proteinase with a pH optimum of 5.2 was associated with this organelle, and is probably responsible for degradation of storage protein. A NADH-dependent cytochrome-c reductase, a membrane marker enzyme with a pH optimum of 8.4, was also present in this organelle fraction.Abbreviations LPA for l-lysine-p-nitroanilide - LPAase for the peptidase which hydrolyzes this peptide This work was supported in part by the National Science Foundation Grant GB-17543, and published as Journal Article No. 5736 of the Michigan Agricultural Experiment Station.Supported by a Deutsche Forschungsgemeinschaft Fellowship.