Dipeptidyl Peptidase 9 (DPP9)?is a cytosolic serine protease that cleaves N-terminal dipeptides from substrates, regulating immune responses, cell survival, and energy metabolism. As a member of the DPP4 family, it modulates inflammatory signaling and plays roles in cancer progression and metabolic disorders. DPP9's inhibition of NLRP1 inflammasome activation highlights its importance in immune regulation.?DPP9 has been reported to interact with HRAS, potentially influencing MAPK/ERK signaling, though its precise role in RAS-driven tumorigenesis requires further investigationThus a functional ELISA assay was conducted to detect the interaction of recombinant mouse DPP9 and recombinant human HRAS. Briefly, DPP9 was diluted serially in PBS with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to HRAS-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-DPP9 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 DPP9 and recombinant human HRAS was shown in Figure 1, the EC50?for this effect is 0.06 μg/mL.