How is the determination of the activity of prolyl endopeptidase enzyme in the synthetic substrate Z-Gly-Pro-pNA? I'd appreciate any protocol proposal.
The colored product is 4-nitroanilide. You can prepare a standard curve using this product to determine how the absorbance changes as the product accumulates under your specific assay conditions (the extinction coefficient in Beer's Law). Use this to convert your absorbance measurements in the enzyme reactions to product concentrations.