enterokinaz

Enterokinase, also known as enteropeptidase, is a secreted serine protease of the mammalian small intestine. It is produced by cells at the brush border of the duodenum and functions to activate pancreatic digestive enzymes by proteolytic cleavage. Specifically, enterokinase cleaves the activation peptide after the lysine residue in the sequence Asp-Asp-Asp-Asp-Lys (DDDDK), thereby converting trypsinogen to active trypsin. Active trypsin then activates other zymogens, including chymotrypsinogen, proelastase, and procarboxypeptidases.

Enterokinase is synthesized as an inactive zymogen and is activated by proteolytic processing. It is a single-chain enzyme that is cleaved into a heavy and a light chain held by disulfide bonds; it belongs to the serine proteases with a catalytic triad of histidine, aspartate, and serine. The enzyme operates best at near-neutral to slightly basic pH and can require calcium ions for stability in some preparations.

In molecular biology, enterokinase is widely used to remove purification tags from recombinant proteins. Fusion proteins are engineered to include the DDDDK recognition sequence so that treatment with enterokinase releases the mature protein. Conditions are chosen to promote specific cleavage with minimal non-specific proteolysis, and commercial preparations are available in various forms for different workflows.

Commercial preparations derive from porcine or bovine sources or are produced recombinantly. The spelling enterokinaz is a common misspelling of enterokinase.