4.7. Enzyme Activity Inhibition Assay

The inhibition effects of antibodies on enzyme activity were determined by an Elastase Inhibitor Screening Kit (Sigma-Aldrich). Briefly, antibodies were diluted to the desired concentration by assay buffer, then 50 μL of neutrophil elastase solution was added and incubated at 37 °C for 45 min. The SPCK NE inhibitor was used as positive control. After incubation, 25 μL of substrate solution was added to each reaction well and the fluorescence was measured in kinetic mode for 30 min. The result was calculated by %Relative inhibition.