title: Guinea pig chymase is leucine-specific: a novel example of functional plasticity in the chymase/granzyme family of serine peptidases.
abstract: To explore guinea pigs as models of chymase biology, we cloned and expressed the guinea pig ortholog of human chymase. In contrast to rats and mice, guinea pigs appear to express just one chymase, which belongs to the alpha clade, like primate chymases and mouse mast cell protease-5. The guinea pig enzyme autolyzes at Leu residues in the loop where human chymase autolyzes at Phe. In addition, guinea pig alpha-chymase selects P1 Leu in a combinatorial peptide library and cleaves Ala-Ala-Pro-Leu-4-nitroanilide but has negligible activity toward substrates with P1 Phe and does not cleave angiotensin I. This contrasts with human chymase, which cleaves after Phe or Tyr, prefers P1 Phe in peptidyl 4-nitroanilides, and avidly hydrolyzes angiotensin I at Phe8 to generate bioactive angiotensin II. The guinea pig enzyme also is inactivated more effectively by alpha1-antichymotrypsin, which features P1 Leu in the reactive loop. Unlike mouse, rat, and hamster alpha-chymases, guinea pig chymase lacks elastase-like preference for P1 Val or Ala. Partially humanized A216G guinea pig chymase acquires human-like P1 Phe- and angiotensin-cleaving capacity. Molecular models suggest that the wild type active site is crowded by the Ala216 side chain, which potentially blocks access by bulky P1 aromatic residues. On the other hand, the guinea pig pocket is deeper than in Val-selective chymases, explaining the preference for the longer aliphatic side chain of Leu. These findings are evidence that chymase-like peptidase specificity is sensitive to small changes in structure and provide the first example of a vertebrate Leu-selective peptidase.
authors: Cardiovascular Research Institute, University of California, San Francisco, California 94143, USA. george.caughey@ucsf.edu
authors: George H
authors: GH
authors: Caughey
authors: Jeremy
authors: J
authors: Beauchamp
authors: Daniel
authors: D
authors: Schlatter
authors: Wilfred W
authors: WW
authors: Raymond
authors: Neil N
authors: NN
authors: Trivedi
authors: David
authors: D
authors: Banner
authors: Harald
authors: H
authors: Mauser
authors: Jürgen
authors: J
authors: Fingerle
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D053818:Chymases / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology; D053804:Granzymes / Q000737:chemistry*; D006168:Guinea Pigs; D006801:Humans; D007930:Leucine / Q000737:chemistry*; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D010447:Peptide Hydrolases / Q000737:chemistry*; D051381:Rats; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000737:chemistry*; D013045:Species Specificity
chemical_list: D004791:Enzyme Inhibitors; D012694:Serine; D010447:Peptide Hydrolases; D053804:Granzymes; D053818:Chymases; D007930:Leucine