Carboxypeptidases and carboxypeptidase inhibitor in tumor-bearing animals; a possible blood test for neoplasia.

Carboxypeptidase is here defined as that en zyme, found in a wide variety of tissues, which hydrolyzes chloracetyl-L-tyrosine, with the pro duction of acid groups and free tyrosine. The dis tribution and properties of this enzyme were recently described by us (1), and it was pointed out not only that two forms of the enzyme can be detected but that there can also be detected a naturally occurring inhibitor for one of these forms. We wish to report here deviations from nor malcy that we have found in this carboxypeptidase-carboxypeptidase inhibitor system in certain animal tumors and in the blood of tumor-bearing animals. We further wish to suggest the possibility that the blood changes may serve as a qualitative test for the presence of malignancy.