Determination of serum procarboxypeptidase A concentrations in healthy human adults.

Clostripain (EC 3.4.22.8) has been shown to be superior to trypsin as a means of activating serum procarboxypeptidase A. With this activation and a previously described assay for carboxypeptidase A it has been possible to determine the concentration of procarboxypeptidase A in human serum. In order to establish a baseline in the healthy adult a survey of the procarboxypeptidase A content of the serum of 66 blood donors was carried out. An average value of 9.7 microg/l was found for the proenzyme. This is in sharp contrast to a mean of 0.34 microg/l for the free enzyme present in serum that was not treated with clostripain [1].