Enteropeptidase (Enterokinase, EC 3.4.21.9) is a serine protease involved in activation of trypsinogen to trypsin, which in turn results in the activation of various digestive enzymes. It recognizes a highly specific amino acid sequence `DDDDK' and cleaves after the lysine residue. High specific activity of Enteropeptidase has been utilized in cleaving a variety of native or fusion protein tags containing the above recognition motif. In Biovision's Enteropeptidase Activity Assay Kit, we have utilized a peptide substrate containing the Enteropeptidase recognition sequence along with a fluorescent label `AFC'. Enteropeptidase catalyzes the cleavage of this substrate and releases the AFC molecule, which can be easily quantified by measuring it