Hydrolysis of Crystalloid Storage Protein in Castor Bean Seed Endosperm During and Following Germination

Hydrolysis of the insoluble crystalloid storage proteins ofcastor bean endosperm during germination released buffer-solublepolypeptides with molecular weights in the presence of sodiumdodecyl sulphate of 30000–40000. These polypeptides appearto be dimers since the addition of 2-mercaptoethanol decreasestheir molecular weights to 15000–22000. Hydrolysis ofthe crystalloid proteins was detected 12–18 h after seedimbibition (HAI), which is before the completion of germination;maximum rates were attained at 30 HAI. During this period, parallelincreases in free amino acids were observed. Hydrolysis of thecrystalloid proteins during early germination was insensitiveto cycloheximide treatment and therefore did not require newlysynthesized proteases. Hydrolysis was effected by proteaseswhich were made in an inactive form during seed developmentand activated upon seed imbibition. Key words: Castor bean, crystalloid storage protein hydrolysis, seed germination, endosperm