Enteropeptidase

Enteropeptidase or enterokinase is an enzyme involved in human digestion. It is produced by cells in the duodenum wall, and is secreted from duodenum's glands, the crypts of Lieberkühn, whenever ingested food enters the duodenum from the stomach. Enteropeptidase has the critical job of turning trypsinogen (a zymogen) to trypsin, indirectly activating a number of pancreatic digestive enzymes.

Enteropeptidase is a serine protease enzyme. Enteropeptidase is a part of the Chymotrypsin-clan of serine proteases, and is structurally similar to these proteins.

Reaction
The reaction catalysed by Enteropeptidase:

trypsinogen → trypsin + octapeptide

Enterokinase cleaves after Lysine if the Lys is preceded by four Asp and not followed by a Pro.

Nomenclature
Despite its older name of enterokinase, the enzyme is not a kinase, since it activates its substrate by cleavage and not phosphorylation.

Genetics
Enteropeptidase is encoded by the PRSS7 (serine protease-7 gene) or ENTK gene on the 21st chromosome (21q21).

Isolated cases of enterokinase deficiency have been reported.