Chemical mechanisms for cytochrome P-450 oxidation: spectral and catalytic properties of a manganese-substituted protein.
AUTOR(ES)
Gelb, M H
RESUMO
Bacterial cytochrome P-450 induced by camphor (P-450cam) is reconstituted with manganese-protoporphyrin IX, yielding an enzyme that displays unique spectral properties relative to previously characterized manganese-porphyrin systems. The nitric oxide complex of the manganese(II)-protein shows a hyper-metalloporphyrin spectrum suggestive of thiolate ligation to the porphyrin-bound manganese ion. In the presence of iodosobenzene as a source of active oxygen, manganese-substituted cytochrome P-450cam serves as a catalyst for the epoxidation of an enzyme-bound olefin substrate. This reactivity proceeds through a spectrally detectable intermediate that resembles the manganese(V)-oxo complexes that have been well documented with model systems employing artificial manganese-metalloporphyrins in organic solution. Interestingly, manganese-substituted cytochrome-P-450cam shows no hydroxylation activity either in the reconstituted camphor hydroxylase system with pyridine nucleotide or in the presence of iodosobenzene and the Mn(III) form of the protein.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=346989Documentos Relacionados
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