Figure 1.

Measurement of different forms of the CPB2 gene product. The zymogen procarboxypeptidase U (proCPU) (1) can be measured with antigen- or activity-based assays. Carboxypeptidase U (CPU) activation can also be determined. Upon activation with thrombin, the thrombin-thrombomodulin (TM) complex, or plasmin, the activation peptide (AP; 2) is released and can be measured with an antigen-based assay. The active enzyme CPU can be directly measured by enzymatic assays (3). The active enzyme CPU is thermally inactivated into CPUi (4) which can be measured with antigen-based assays that detect both CPU and CPUi simultaneously (5).