PDE5A-1E is a splice variant of phosphodiesterase 5A (PDE5A), a key member of the PDE superfamily that hydrolyzes cyclic guanosine monophosphate (cGMP), a critical second messenger regulating smooth muscle relaxation, vascular tone and cellular signaling. Expressed prominently in vascular smooth muscle, penile tissue and platelets, PDE5A-1E retains the core catalytic domain of wild-type PDE5A, enabling it to degrade cGMP and modulate downstream physiological processes like penile erection and blood pressure regulation. As a unique isoform, it has distinct tissue expression patterns and functional characteristics compared to other PDE5A variants, making it a vital therapeutic target for erectile dysfunction and pulmonary arterial hypertension. Additionally, PDE5A-1E physically interacts with APRT, forming a protein complex with unclear functional implications.Thus a functional ELISA assay was conducted to detect the interaction of recombinant human PDE5A-1E and recombinant human APRT. Briefly, PDE5A-1E was diluted serially in PBS with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to APRT-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-PDE5A-1E pAb, then aspirated and washed 3 times. After incubas. 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 human PDE5A-1E and recombinant human APRT was shown in Figure 1, the EC50?for this effect is 0.128μg/mL.