title: Redox-linked spin-state changes in the di-haem cytochrome c-551 peroxidase from Pseudomonas aeruginosa.
abstract: Magnetic-c.d., e.p.r. and optical-absorption spectra are reported for the half-reduced form of Pseudomonas aeruginosa cytochrome c-551 peroxidase, a di-haem protein, and its fluoride derivative. Comparison of this enzyme species with oxidized peroxidase shows the occurrence of spin-state changes at both haem sites. The high-potential haem changes its state from partially high-spin to low-spin upon reduction. This is linked to a structural alteration at the ferric low-potential haem group, causing it to change from low-spin to high-spin. Low-temperature spectra demonstrate photolysis of an endogenous ligand of the high-potential haem. In addition, an inactive form of enzyme is examined in which the structural change at the ferric low-potential haem does not occur on reduction of the high-potential haem.
mesh_terms: D002942:Circular Dichroism; D003578:Cytochrome-c Peroxidase; D004578:Electron Spin Resonance Spectroscopy; D010084:Oxidation-Reduction; D010544:Peroxidases; D010782:Photolysis; D011550:Pseudomonas aeruginosa / Q000201:enzymology*; D013055:Spectrophotometry, Infrared; D013696:Temperature
chemical_list: D010544:Peroxidases; D003578:Cytochrome-c Peroxidase