Mediated catalysis of Paracoccus pantotrophus cytochrome c peroxidase by P. pan...

• Author(s): Sousa, P. M. Paes de ; Pauleta, Sofia R. ; Gonçalves, M. L. Simões ; Pettigrew, Graham W. ; Moura, Isabel ; Moura, José J. G. ; Santos, Margarida M. Correia dos
• Date: 2007
• Persistent ID: http://hdl.handle.net/10362/8703
• Origin: Repositório Institucional da UNL
• Subject(s): Pseudoazurin; Cytochrome c peroxidase; Catalysis; Voltammetry; Intermolecular electron transfer
• Document Type: Article
• Language: English

Description

J Biol Inorg Chem (2007) 12:691–698 DOI 10.1007/s00775-007-0219-9 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.