Enteropeptidase (also called enterokinase) is an enzyme produced by cells of the duodenum and involved in human and animal digestion. It is secreted from intestinal glands (the crypts of Lieberkühn) following the entry of ingested food passing from the stomach. Enteropeptidase converts trypsinogen (a zymogen) into its active form trypsin, resulting in the subsequent activation of pancreatic digestive enzymes. Absence of enteropeptidase results in intestinal digestion impairment.Enteropeptidase is a serine protease (EC 3.4.21.9) consisting of a disulfide-linked heavy-chain of 82-140 kDa that anchors enterokinase in the intestinal brush border membrane and a light-chain of 35–62 kDa that contains the catalytic subunit. Enteropeptidase is a part of the chymotrypsin-clan of serine proteases, and is structurally similar to these proteins.