Bacterial Sortase Substrate III, Abz/DNP is an internally quenched fluorescent peptide substrate. Staphylococcus aureus transpeptidase sortase A (SrtA) reacts with its native substrate Bacterial Sortase Substrate III, Abz/DNP, cleaving it and catalyzing the formation of an amide bond between the carboxyl group of threonine and the amino group of cell-wall crossbridges. Cleavage of this substrate can be monitored at Ex/Em=320 nm/420 nm.