Chymotrypsin C (CTRC) is a member of the peptidase S1 family. The encoded protein is a serum calcium-decreasing factor that has chymotrypsin-like protease activity. It regulates activation and degradation of trypsinogens and procarboxypeptidases by targeting specific cleavage sites within their zymogen precursors. Has chymotrypsin-type protease activity and hypocalcemic activity. Besides, Plasminogen Activator, Urokinase Receptor (uPAR) has been identified as an interactor of CTRC, thus a binding ELISA assay was conducted to detect the interaction of recombinant rat CTRC and recombinant rat uPAR. Briefly, CTRC were diluted serially in PBS, with 0.01%BSA (pH 7.4). Duplicate samples of 100uL were then transferred to uPAR-coated microtiter wells and incubated for 2h at 37℃. Wells were washed with PBST and incubated for 1h with anti- CTRC pAb, then aspirated and washed 3 times. After incubation with HRP labelled secondary antibody, wells were aspirated and washed 3 times. With the addition of substrate solution, wells were incubated 15-25 minutes at 37℃. Finally, add 50µL stop solution to the wells and read at 450nm immediately. The binding activity of of CTRC and uPAR was shown in Figure 1, and this effect was in a dose dependent manner.