Contactin-associated protein-like 2 (CNTNAP2, also called CASPR2) is a transmembrane neuronal adhesion molecule belonging to the neurexin family. It is highly expressed in the central and peripheral nervous systems, localizing at myelinated axon juxtaparanodes to stabilize potassium channels and support saltatory conduction. CNTNAP2 is critical for synapse formation, axon–glia interactions, and cortical development; its mutations are strongly linked to autism spectrum disorder, epilepsy, language impairment, and other neurodevelopmental conditions. As one of the largest human genes, CNTNAP2 modulates neuronal excitability and network homeostasis, making it a key biomarker for neuropsychiatric disorders. CNTNAP2 associates with DPP6 as part of the Kv4 potassium channel complex to regulate neuronal surface expression and gating kinetics.Briefly, DPP6 was diluted serially in PBS with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to CNTNAP2-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-DPP6 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 450/630nm immediately. Measured by its binding ability in a functional ELISA. When Recombinant human CNTNAP2 is lmmobilized at 2 µg/mL(100 µLwell), the concentration of DPP6 that produces 50% optimal bindingresponse is found to be approximately 0.009 µg/mL.