Platelet/Endothelial Cell Adhesion Molecule (PECAM1), also known as CD31, is a transmembrane glycoprotein which belongs to the immunoglobulin superfamily. PECAM1 is widely expressed in various tissues, including blood vessels, the heart, lungs, and the brain and plays an important role in intercellular adhesion, cell migration, platelet function regulation and immune response.Abnormal expression of PECAM-1 is also associated with a variety of diseases, such as atherosclerosis, inflammation and blood diseases. Besides, Protein Tyrosine Phosphatase, Non Receptor Type 6 (PTPN6) has been identified as an interactor of PECAM1, thus a functional binding ELISA assay was conducted to detect the interaction of recombinant human PECAM1 and recombinant human PTPN6. Briefly, biotin-linked PECAM1 were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100 ul were then transferred to PTPN6-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST 3 times and incubation with Streptavidin-HRP for 30min, then 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 nm immediately. The binding activity of recombinant human PECAM1 and recombinant human PTPN6 was shown in Figure 1, the EC50?for this effect is 1.69 ug/mL.