Carboxypeptidase Activity of Tomato Fruit during the Ripening Process and Some Enzymatic Properties

Carboxypeptidase activity of tomato fruit reached a maximum at an early period of ripening. During storage of the fruit at 25°C, the enzyme activity decreased, accompanied by a fall of the pH value of the sap.The enzyme was apparently localized in the soluble fraction, as determined by differential centrifugation.The enzyme was optimally active at pH 5.0 ~ 5.5, was most stable at pH 4.5 ~ 6.5, and was strongly inhibited by DFP and HgCl2, but not by EDTA and 1,10-phenanthroIine. Z-dipeptides containing arginine, proline and several neutral amino acids were hydrolyzed by the enzyme.The similarity of the enzymatic properties of the present enzyme to those of other plant carboxypeptidases and pig kidney cathepsin A is also discussed.