Some Properties of Carboxypeptidases in Germinating Rice Seeds and Rice Leaves

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Abstract
Germinating rice contained three carboxypeptidases or carboxypeptidase-like enzymes which hydrolyzed CPA (carbobenzoxy-l-phenylalanyl-l-alanine) at different pH ranges. The three CPA hydro lases which acted optimally at pH 4, 5 ~ 5.5, and 7. were tentatively termed CPAase-4, CPAase-5, and CPAase-7 respectively. CPAase-4 was contained in resting seeds and endosperms of germinating seeds. Its activity was maximum in resting seeds and gradually decreased during germination. CPAase-5 was absent in resting seeds, and appeared in endosperms and seedlings in the later stages after germinaion. This enzyme was predominant in mature plant leaves. CPAase-7 was detected in the young shoots and young roots during a limited period of germination. Enzymatic properties of CPAase-5 partially purified from rice leaves were very similar to those of carboxypeptidases in various plants.