Cleavage of peptide-4-nitroanilide substrates with varying chain length by human leukocyte elastase

Two series of substrates with the formulas H-Alan-Val-4-nitroanilide and 3-carboxypropionyl-Alan-Val-4-nitroanilide (n = 1, 2 and 3) were synthesized. Elongation of the peptide chain yields increasingly better substrates for human leukocyte elastase both in terms of Km and kcat. These results indicate an extended substrate binding site for the enzyme.