NEU (Sialidase-1) is an enzyme that catalyzes the removal of sialic acid (N-acetylneuraminic acid) moities from glycoproteins and glycolipids. In the lysosome, this enzyme is part of a heterotrimeric complex together with beta-galactosidase and cathepsin A (CTSA). Thus a binding ELISA assay was conducted to detect the interaction of recombinant human NEU and recombinant human CTSA. Briefly, NEU were diluted serially in PBS, with 0.01%BSA (pH 7.4). Duplicate samples of 100uL were then transferred to CTSA-coated microtiter wells and incubated for 2h at 37°C. Wells were washed with PBST and incubated for 1h with anti-NEU pAb, then aspirated and washed 3 times. After incubation with HRP labelled secondary antibody, wells were aspirated and washed 3 times. With the addition of substrate solution, wells were incubated 15-25 minutes at 37°C. Finally, add 50μL stop solution to the wells and read at 450nm immediately. The binding activity of NEU and CTSA was shown in Figure 1, and this effect was in a dose dependent manner.