Alterations of serum carboxypeptidases N and angiotensin-I-converting enzyme in malignant diseases.

The activities of serum carboxypeptidases N (E.C. 3.4.17.3) and serum angiotensin-I-converting enzyme (E.C. 3.4.15.1) were spectrophotometrically measured in patients with hematological disorders and in histologically proven bronchogenic carcinomas. The enzyme activities have been compared with various laboratory parameters. Controls were healthy subjects. No significant sex differences of carboxypeptidases N and angiotensin-I-converting enzyme were found in the healthy controls or in the whole patients' group. The carboxypeptidases N were significantly elevated in patients with lung cancer (p less than 0.0001) compared to the healthy controls. The angiotensin-I-converting enzyme was significantly reduced (p less than 0.0001) in serum of patients with bronchogenic carcinoma. In responders to chemo- and/or radiotherapy, the carboxypeptidases decreased and the angiotensin-I-converting enzyme increased to normal enzyme values. In non-responders to these therapies no change in these enzymes could be observed.