– Enteropeptidase fluorogenic substrate is a substrate for enteropeptidase that contains a 7-amino-4-trifluoromethylcoumarin (AFC) moiety. Enteropeptidase is a serine protease expressed in the proximal small intestine of higher animals that converts inactive trypsinogen to active trypsin by endoproteolytic cleavage.1,2Enteropeptidase recognizes the highly specific amino acid sequence DDDDK on the fluorogenic substrate and cleaves after the lysine residue, releasing the AFC moiety. Enteropeptidase activity is quantified by fluorescent detection of AFC, which displays excitation/emission spectra of 380/500 nm.3