Abz-Ala-Pro-Glu-Glu-Ile-Met-Arg-Arg-Gln-EDDnp is a fluorescence-quenched peptide substrate for human neutrophil elastase (kcat/Km = 531 mM-1s-1). Enzymatic peptide hydrolysis disrupts the Abz:EDDnp donor-acceptor pair allowing fluorescence measurement of Abz (ex = 320 nm; em = 420 nm).