FIGURE 4.

Hydrolysis of substrates in a combinatorial peptide library. Wild type guinea pig chymase, A216G mutant guinea pig chymase, and human chymase were incubated with peptides of sequence QAXXXXAQQG (where X represents random amino acids). Human chymase also was screened with peptides displaying SSVXAXSAPG, with two randomly varying amino acids. The sequences of individual peptides hydrolyzed by the enzymes are shown, with the hydrolysis site (P1) italicized and with variable positions in boldface. Substrate residues with aromatic, acidic, basic, and small aliphatic side chains are color-coded green, red, blue, and yellow, respectively.