The Properties of the Heavy and Light Subunits of Bovine Enterokinase

This research project was concerned with the structure, function, and physiological properties of bovine enterokinase. The light change is the catalytic subunit and contains the histidine-serine-aspartic acid of the active site. The catalytic subunit is obtained as a functional subunit after cleavage of the connecting disulfide using mild reducing conditions. We are studying the amino acid sequence and enzymatic properties of the catalytic subunit. The isolation procedure was improved for bovine enterokinase and for the preparation of the catalytic subunit. These two accomplishments made it possible to obtain sufficient amounts of highly purified enzyme to perform a partial amino-terminal sequence analysis of the light chain and to establish the disulfide content of the chain. The properties of a functional catalytic subunit differed from those found in the past. Milder reaction conditions produced a more native form of the enzyme. The action of the enzyme toward small synthetic substrates and toward the substrate trypsinogen and the protein inhibitor bovine pancreatic trypsin inhibitor were investigated. The specificity characteristics suggested that the heavy subunit may be necessary to form a productive enzyme-substrate complex with the large substrate molecules. Keywords Bovine enterokinase, Amino acids, Enzymes, Enterokinase, Biochemistry.