Mediated catalysis of <Emphasis Type="Italic">Paracoccus pantotrophus</Emphasis> cytochrome <Emphasis Type="Italic">c</Emphasis> peroxidase by <Emphasis Type="Italic">P. pantotrophus</Emphasis> pseudoazurin: kinetics of intermolecular electron transfer |
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Authors: | P M Paes de Sousa S R Pauleta M L Simões Gonçalves G W Pettigrew I Moura M M Correia dos Santos J J G Moura |
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Institution: | (1) ReQuimte, Centro de Química Fina e Biotecnologia, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal;(2) Centro de Química Estrutural, Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal;(3) Royal (Dick) School of Veterinary Studies, University of Edinburgh, Summerhall, Edinburgh, EH9 1QH, UK |
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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 × 105 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. |
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Keywords: | Pseudoazurin Cytochrome c peroxidase Catalysis Voltammetry Intermolecular electron transfer |
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