Carboxypeptidase B2 (CPB2), also known as carboxypeptidase U (CPU) and thrombin-activatable fibrinolysis inhibitor (TAFI), is a member of the peptidase M14 family.
CPB2 is synthesized by the liver and circulates in plasma as a plasminogen-bound zymogen. It can cleave C-terminal arginine or lysine residues from biologically active peptides such as kinins or anaphylatoxins in the circulation thereby regulating their activities and Down-regulates fibrinolysis by removing C-terminal lysine residues from fibrin that has already been partially degraded by plasmin. Besides, Plasminogen (Plg) has been identified as an interactor of CPB2, thus a functional binding ELISA assay was conducted to detect the interaction of recombinant human CPB2 and recombinant mouse Plg. Briefly, CPB2 was diluted serially in PBS with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to Plg-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-CPB2 pAb, then aspirated and washed 3 times. After incubation with HRP labelled secondary antibody for 1h at 37℃, wells were aspirated and washed 5 times. With the addition of substrate solution, wells were incubated 15-25 minutes at 37℃. Finally, add 50 µL stop solution to the wells and read at 450/630 nm immediately. The binding activity of recombinant human CPB2 and recombinant mouse Plg was shown in Figure 1, the EC50 for this effect is 2.9 ug/mL.