Dickkopf Related Protein 1 (DKK1) is a secreted glycoprotein that functions as a key antagonist of the canonical Wnt/β-catenin signaling pathway. It is critically involved in embryonic development, particularly in head formation, and also plays roles in bone remodeling, cancer progression, and immune regulation. Elevated levels of DKK1 are associated with various bone diseases, including osteoporosis, and certain cancers where it suppresses Wnt-mediated cell differentiation and proliferation. DKK1 inhibits Wnt signaling by directly binding to the Wnt co-receptor Low-Density Lipoprotein Receptor-Related Protein 5 (LRP5), thereby preventing the formation of the Wnt-Frizzled-LRP5 complex and subsequent signal transduction.To detect the activity of recombinant DKK1 , a functional ELISA assay was performed to evaluate the interaction between recombinant human DKK1 and recombinant rat LRP5.Briefly, DKK1 were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100ul were then transferred to LRP5-coated microtiter wells and incubated for 2h at 37℃. Wells were washed with PBST and incubated for 1h with anti-DKK1 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 DKK1 and LRP5 was shown in Figure 1, and this effect was in a dose dependent manner.