The solubilization and degradation of pumpkin seed globulin during germination

Pumpkin seed globulin decreased 88% during the first 4 days of germination. This decrease was concomitant with a 2.5 fold increase in water soluble protein which arose directly from the water insoluble globulin. The sequence of solubilization and breakdown of the globulin was followed through 12 days of germination. Pumpkin seed globulin was determined to have subunits of 56,000 daltons, while the new water soluble protein consisted of two proteins, as determined by sodium dodecyl sulfate polyacrylamide electrophoresis; one having a molecular weight of 42,000 daltons and the other 28,000 daltons. Trypsin mimicked the first step of the breakdown by solubilizing pumpkin seed globulin to yield identical digestion products as were obtained in vitro. Maximum proteolytic acitvity, as measured by the release of ninhydrin positive, materials occurred at 6 days of germination, at which time both the concentration of free amino acids and the incorporation of 14C into amino acids increased rapidly. A second proteolytic enzyme system which solubilized the pumpkin seed globulin but did not act on hemoglobin, casein, or bovine serum albumin reached its maximum activity at two days of germination.