The solubilization and degradation of pumpkin seed globulin during germination

Pumpkin seed globulin decreased 88% during the first 4 daysof germination. This decrease was concomitant with a 2.5 foldincrease in water soluble protein which arose directly fromthe water insoluble globulin. The sequence of solubilizationand breakdown of the globulin was followed through 12 days ofgermination. Pumpkin seed globulin was determined to have subunitsof 56,000 daltons, while the new water soluble protein consistedof two proteins, as determined by sodium dodecyl sulfate polyacrylamideelectrophoresis; one having a molecular weight of 42,000 daltonsand the other 28,000 daltons. Trypsin mimicked the first stepof the breakdown by solubilizing pumpkin seed globulin to yieldidentical digestion products as were obtained in vitro. Maximumproteolytic acitvity, as measured by the release of ninhydrinpositive, materials occurred at 6 days of germination, at whichtime both the concentration of free amino acids and the incorporationof ¹⁴C into amino acids increased rapidly. A second proteolyticenzyme system which solubilized the pumpkin seed globulin butdid not act on hemoglobin, casein, or bovine serum albumin reachedits maximum activity at two days of germination. (Received April 17, 1978; )