DESIGN OF KALLIDIN-RELEASING TISSUE KALLIKREIN INHIBITORS BASED ON THE SPECIFICITIES OF THE ENZYMES BINDING SUBSITES

The tissue kallikrein inhibitors reported in the present work were der ived by selectively replacing residues in N-alpha-substituted arginine - or phenylalanine-pNA (where pNA is p-nitroanilide), and in peptide s ubstrates for these enzymes. Phenylacetyl-Arg-pNA was found to be an e fficient inhibitor of human tissue kallikrein (K-i 0.4 mu M) and was n either a substrate nor an inhibitor of plasma kallikrein. The peptide inhibitors having phenylalanine as the P-1 residue behaved as specific inhibitors for kallidin-releasing tissue kallikreins, while plasma ka llikrein showed high affinity for inhibitors containing (p-nitro)pheny lalanine at the same position. The K-i value of the most potent inhibi tor developed, Abz-Phe-Arg-Arg-Pro-Arg-EDDnp [where Abz is o-aminobenz oyl and EDDnp is N-(2,4-dinitrophenyl)ethylenediamine], was 0.08 mu M for human tissue kallikrein. Progress curve analyses of the inhibition of human tissue kallikrein by benzoyl-Arg-pNA and phenylacetyl-Phe-Se r-Arg-EDDnp indicated a single-step mechanism for reversible formation of the enzyme-inhibitor complex.