Angiotensin I Converting Enzyme (ACE) is a zinc-dependent metalloprotease that plays a crucial role in the renin-angiotensin system (RAS), regulating blood pressure and fluid balance. ACE converts the inactive angiotensin I into the potent vasoconstrictor angiotensin II, which increases blood pressure by constricting blood vessels and stimulating aldosterone secretion. Additionally, ACE degrades bradykinin, a vasodilator, further promoting hypertension.Besides,Renin (REN) has been identified as an interactor of ACE, thus a functional binding ELISA assay was conducted to detect the interaction of recombinant human ACE and recombinant human REN . Briefly, biotin-linked ACE were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100μl were then transferred to REN-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 50µl stop solution to the wells and read at 450nm immediately. The binding activity of ACE and REN was shown in Figure 1, the EC50 for this effect is1.035µg/mL.