Trypsinogen is a precursor enzyme, or zymogen, secreted by the exocrine part of the pancreas, moving to the small intestine after secretion. In the duodenum, it is activated into the enzyme trypsin by enteropeptidase, which is found in the intestinal mucosa. Trypsinogen is found in pancreatic juice, along with amylase, lipase, and chymotrypsinogen. Once activated, the trypsin can activate more trypsinogen into trypsin. Trypsin cleaves peptide bond on carboxyl side of basic amino acids. Serum trypsinogen is measured using a blood test. High levels are seen in acute pancreatitis, and cystic fibrosis.