Lysosomal Acid Lipase (LIPA) is a crucial enzyme within the lysosomes that hydrolyzes cholesteryl esters and triglycerides into free cholesterol and free fatty acids. This process is vital for cellular lipid metabolism and energy homeostasis. Deficiencies in LIPA activity lead to severe lipid storage disorders, such as Wolman disease and Cholesteryl Ester Storage Disease (CESD), characterized by the massive accumulation of lipids in the liver, spleen, and other organs. Regarding its interaction, LIPA does not directly bind to Apolipoprotein B (APOB); instead, it interacts with and degrades the lipid core of Low-Density Lipoprotein (LDL) particles, of which APOB is the primary structural protein component.Besides,APOB has been identified as an interactor of LIPA, thus a functional binding ELISA assay was conducted to detect the interaction of recombinant rat LIPA and recombinant pig APOB. Briefly, LIPA was diluted serially in PBS with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to APOB-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-LIPA 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 rat LIPA and recombinant pig APOB was shown in Figure 1, the EC50 for this effect is 1.06326µg/mL.