Enterokinase (EK) is a mammalian duodenal protease consisting of a heavy chain (82–140 kDa) anchoring to the intestinal brush border and a light chain (35–62 kDa) containing the catalytic subunit. It specifically cleaves after the DDDDK sequence. Recombinant bovine enterokinase (rBoEK) exhibits higher activity than native forms and is widely used in biochemical applications.