Cluster Of Differentiation 38 (CD38), also known as cADPRH (cyclic ADP-ribose hydrolase), is a multifunctional transmembrane glycoprotein expressed in various cell types, including immune cells, endothelial cells, and hematopoietic cells. Encoded by the CD38 gene, it exhibits dual roles as an enzyme and a receptor. As an enzyme, CD38 catalyzes the metabolism of NAD , producing second messengers like cyclic ADP-ribose (cADPR) and ADPR, which regulate calcium signaling. As a receptor, it binds to ligands such as CD31, mediating cell adhesion, migration, and immune modulation. Abnormal CD38 expression is associated with multiple diseases, including hematological malignancies, autoimmune disorders, and metabolic diseases. Its diverse functions make it a critical target for therapeutic development, particularly in cancer immunotherapy and metabolic disorder treatments.To detect the activity of recombinant CD38 , a functional ELISA assay was performed to evaluate the interaction between recombinant mouse CD38 and recombinant human SIRT1.Briefly, CD38 was diluted serially in PBS with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to SIRT1-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-CD38 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. The binding activity of recombinant mouse CD38 and recombinant human SIRT1 was shown in Figure 1, the EC50?for this effect is 4.33259 μg/mL.