CLEAVAGE SPECIFICITY OF PORCINE FOLLIPSIN

Follipsin purified from the follicular fluid of porcine ovaries was st udied for its specificity against various synthetic and peptide substr ates. The enzyme cleaved only by an endopeptidase activity at the amid e and peptide bonds of Arg-X, indicating strict specificity of the S-1 pocket for arginine. The specificity for pocket S-2 appears to favor either hydrophobic or basic side chains. A 10-residue peptide containi ng a portion of the activation site of human tissue plasminogen activa tor was synthesized and tested with the enzyme, The peptide was cleave d by follipsin at the Arg-Ile bond, as expected from the specificity d educed above. Furthermore, the enzyme successfully converted single-ch ain precursor tissue plasminogen activator (sctPA) to its active, two- chain form by cleaving the corresponding peptide bond, Comparison of t he rates of single-chain precursor tissue plasminogen activator activa tion and tissue plasminogen activator peptide hydrolysis revealed that the former is a more efficient substrate than the latter.