Control of the spin state of the peroxidatic haem by calcium ions in cytochromec peroxidase fromParacoccus denitrificans: A1H NMR study

Autor: Susana Prazeres, Celia F. Goodhew, Raymond Gilmour, Isabel Moura, José J. G. Moura, Graham W. Pettigrew
Rok vydání: 1993
Předmět:
Zdroj: Magnetic Resonance in Chemistry. 31:S68-S72
ISSN: 1097-458X
0749-1581
Popis: Cytochrome c peroxidase from Paracoccus denitrificans LMD 52.44 was recently identified. The enzyme contains two c-type haems: one is reducible physiologically by cytochrome c550 from the same organism or non-physiologically by ascorbate (high-potential haem) and the other by dithionite (low-potential haem). The enzymatically active form of the peroxidase is the half-reduced enzyme state, in which the high-potential haem is in the iron(II) state and the low-potential haem is in the iron(III) state. It was found that the two haems interact and that the enzyme binds calcium ions near the haem sites which are necessary to promote its activation. In the oxidized form, the high-potential haem is in a high-spin and the low-potential haem is in a low-spin state. The half-reduction of the enzyme with ascorbate-diaminodurol changes the high-potential haem (high-spin) into a low-spin state and the low-potential haem converts from a low- into a high-spin state. This high-spin conversion of the low-potential haem is induced by the presence of calcium ions. These processes of reduction and spin state change can be easily resolved in time by removing the calcium from the enzyme using EDTA, facilitating the observation of the intermediate form by NMR.
Databáze: OpenAIRE
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