Carboxypeptidase (CPase) in the endosperm of castor bean (Ricinus communis L.) showed high activity at day 4 and 7 on germination. From the behavior of CPases on CM-cellulose column chromatography, the early stage CPases, which appeared before 4 day germination, were different from the later stage CPases which appeared after 6 day. Probably the former arised from ungerminated seeds and the latter was synthesized during the germination. The early stage endosperm of small grain castor bean contained three species of CPases, contrary to this, these of large grain contained only one species. With respect to the small grain castor bean, the changes of both percentage of germination and CPase activity during the germination did not observed even after one year storage. In the case of old large grain castor bean, the decrease in early stage CPase activity was associated with the decline of percentage of germination. The exidence suggested that the early stage CPase plays the important role for early stage of germination. The early stage CPase had optimum pH at 5.0 and molecular weight of 110,000. The substrate specificity was carboxypeptidase A type.
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