STRUCTURAL FACTORS PROVIDING FOR THE HIGH SPECIFICITY OF ENTEROPEPTIDASE

The effects of structural modification upon the specificity of enterop eptidase were studied. A variation in the unique specificity of the en zyme was shown to be the result of an autolysis caused by the enzyme's loss of calcium ions. The cleavage sites of the autolysis were determ ined. A truncated enzyme containing the C-terminal fragment of its hea vy chain (466-800 residues) and the intact light chain were shown to b e the products of autolysis. The kinetic parameters of the hydrolysis of trypsinogen, a recombinant protein, and a peptide substrate with bo th forms of enteropeptidase were determined. Conditions were found tha t can help regulate the transition of the native enzyme into the trunc ated form. A hypothesis was proposed concerning the autoactivational c haracter of proenteropeptidase processing.