title: Chemical mechanisms for cytochrome P-450 oxidation: spectral and catalytic properties of a manganese-substituted protein.
abstract: 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.
mesh_terms: D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D006420:Hemeproteins / Q000378:metabolism; D007700:Kinetics; D008345:Manganese / Q000494:pharmacology*; D011549:Pseudomonas / Q000378:metabolism; D013053:Spectrophotometry
chemical_list: D006420:Hemeproteins; D008345:Manganese; D003577:Cytochrome P-450 Enzyme System