Trypsinogen (EC 3.4.23.18/20/21/23/24/26) () is the precursor form or zymogen of trypsin, a digestive enzyme. Produced by the pancreas, it is found in pancreatic juice, along with amylase, lipase, and chymotrypsinogen. It is activated by enteropeptidase, which is found in the intestinal mucosa, to form trypsin. Once activated, the trypsin can activate more trypsinogen into trypsin.  Trypsin cleaves the peptide bond on the carboxyl side of basic amino acids such as arginine and lysine.