Catalytic properties of thimet oligopeptidase H600A mutant.
Thimet oligopeptidase (EC 3.4.24.15, TOP) is a metallo-oligopeptidase that participates in the intracellular metabolism of peptides. Predictions based on structurally analogous peptidases (Dcp and ACE-2) show that TOP can present a hinge-bend movement during substrate hydrolysis, what brings some residues closer to the substrate. One of these residues that in TOP crystallographic structure are far from the catalytic residues, but, moves toward the substrate considering this possible structural reorganization is His(600). In the present work, the role of His(600) of TOP was investigated by site-directed mutagenesis. TOP H600A mutant was characterized through analysis of S(1) and S(1)' specificity, pH-activity profile and inhibition by JA-2. Results showed that TOP His(600) residue makes important interactions with the substrate, supporting the prediction that His(600) moves toward the substrate due to a hinge movement similar to the Dcp and ACE-2. Furthermore, the mutation H600A affected both K(m) and k(cat), showing the importance of His(600) for both substrate binding and/or product release from active site. Changes in the pH-profile may indicate also the participation of His(600) in TOP catalysis, transferring a proton to the newly generated NH2-terminus or helping Tyr(605) and/or Tyr(612) in the intermediate oxyanion stabilization.
Departamento de Biofísica, Universidade Federal de São Paulo, 04044-020 São Paulo, SP, Brazil.
Maurício F M
MF
Machado
Marcelo F
MF
Marcondes
Vanessa
V
Rioli
Emer S
ES
Ferro
Maria A
MA
Juliano
Luiz
L
Juliano
Vitor
V
Oliveira
D000818:Animals; D002384:Catalysis; D006639:Histidine / Q000737:chemistry / Q000235:genetics; D008666:Metalloendopeptidases / Q000737:chemistry* / Q000235:genetics; D016297:Mutagenesis, Site-Directed; D009154:Mutation
D006639:Histidine; D008666:Metalloendopeptidases; C022510:thimet oligopeptidase