title: The amino-terminal sequence of the catalytic subunit of bovine enterokinase.
abstract: Bovine enterokinase (enteropeptidase) is a serine protease and functions as the physiological activator of trypsinogen. The enzyme has a heavy chain (115 kD) covalently linked to a light or catalytic subunit (35 kD). The amino acid composition showed that the light chain has nine half-cystine residues (four as intramolecular disulfides) and that one half-cystine was in a disulfide link between the light and heavy subunits. The amino-terminal 27 residues of the S-vinylpyridyl derivative of the light chain were determined by gas-phase Edman degradation. The sequence has homologies with other serine proteases containing one or two chains. The homologies suggest that the catalytic subunit has the same three-dimensional structure and, therefore, the same mechanism of enzymatic action as pancreatic chymotrypsin, trypsin, and elastase. The presence of the conserved amino-terminal activation peptide sequence (IVGG) shows that enterokinase must have a zymogen precursor and that the two-chain enzyme arises from limited proteolysis during posttranslational processing.
authors.affiliation: Department of Chemistry, Purdue University, West Lafayette, Indiana 47907.
authors.forename: A
authors.initials: A
authors.lastname: Light
authors.forename: H
authors.initials: H
authors.lastname: Janska
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D004765:Enteropeptidase / Q000737:chemistry*; D008969:Molecular Sequence Data; D010669:Phenylthiohydantoin; D012689:Sequence Homology, Nucleic Acid; D012697:Serine Endopeptidases / Q000737:chemistry; D009764:o-Phthalaldehyde
chemical_list: D010669:Phenylthiohydantoin; D009764:o-Phthalaldehyde; D012697:Serine Endopeptidases; D004765:Enteropeptidase