– Enterokinase (EK) is a serine protease produced in the duodenum and involved in mammalian digestion. It activates trypsinogen to trypsin, thereby indirectly initiating the activation of pancreatic digestive enzymes. EK specifically cleaves after the recognition sequence Asp-Asp-Asp-Asp-Lys, but is inactive if a proline follows the cleavage site. This recombinant bovine enterokinase is the light chain catalytic subunit, comprising a single glycosylated polypeptide chain corresponding to residues Ile801–His1035 of the native protein (Accession # P98072). Expressed in Pichia pastoris under animal-free conditions, the enzyme is highly active and suitable for applications in drug and vaccine development. A C-terminal 6×His tag is included to allow efficient removal by Ni²⁺ affinity chromatography following cleavage reactions.