title: Mediated catalysis of Paracoccus pantotrophus cytochrome c peroxidase by P. pantotrophus pseudoazurin: kinetics of intermolecular electron transfer.
abstract: This work reports the direct electrochemistry of Paracoccus pantotrophus pseudoazurin and the mediated catalysis of cytochrome c peroxidase from the same organism. The voltammetric behaviour was examined at a gold membrane electrode, and the studies were performed in the presence of calcium to enable the peroxidase activation. A formal reduction potential, E (0)', of 230 +/- 5 mV was determined for pseudoazurin at pH 7.0. Its voltammetric signal presented a pH dependence, defined by pK values of 6.5 and 10.5 in the oxidised state and 7.2 in the reduced state, and was constant up to 1 M NaCl. This small copper protein was shown to be competent as an electron donor to cytochrome c peroxidase and the kinetics of intermolecular electron transfer was analysed. A second-order rate constant of 1.4 +/- 0.2 x 10(5) M(-1) s(-1) was determined at 0 M NaCl. This parameter has a maximum at 0.3 M NaCl and is pH-independent between pH 5 and 9.
authors.affiliation: ReQuimte, Centro de Química Fina e Biotecnologia, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.
authors.forename: P M Paes
authors.initials: PM
authors.lastname: de Sousa
authors.forename: S R
authors.initials: SR
authors.lastname: Pauleta
authors.forename: M L Simões
authors.initials: ML
authors.lastname: Gonçalves
authors.forename: G W
authors.initials: GW
authors.lastname: Pettigrew
authors.forename: I
authors.initials: I
authors.lastname: Moura
authors.forename: M M Correia
authors.initials: MM
authors.lastname: Dos Santos
authors.forename: J J G
authors.initials: JJ
authors.lastname: Moura
mesh_terms: D001400:Azurin / Q000378:metabolism*; D002384:Catalysis; D003578:Cytochrome-c Peroxidase / Q000378:metabolism*; D004563:Electrochemistry; D004566:Electrodes; D004573:Electrolytes; D004579:Electron Transport / Q000502:physiology*; D006861:Hydrogen Peroxide / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D007700:Kinetics; D042084:Paracoccus pantotrophus / Q000201:enzymology*
chemical_list: D004573:Electrolytes; D007202:Indicators and Reagents; C047163:pseudoazurin; D001400:Azurin; D006861:Hydrogen Peroxide; D003578:Cytochrome-c Peroxidase