Abstract
Cobalt-substituted cytochrome P450 cam was recently reconstituted by Wagner et al ( J. Biol. Chem. 256, 6266, (1981)). A model of its coordination site was constructed to determine the mode of axial coordination of the native enzyme. Complexes were prepared from cobalt porphyrins (cobalt-protoporphyrin IX (CoPPIX), cobalt- meso-tetraphenylporphyrin, cobalt-γ-laurylpyridyl triphenylporphyrin, and cobalt-octaethylporphyrin), thioglycolate ester, and tetramethylammonium hydroxide in organic solvents. Complexes prepared in an organic solvent such as CHC1 3 under air at room temperature exhibited a stable Soret hyperporphyrin spectrum characterized by split Soret bands, especially like that of the thiol-Co-P450 cam complex Comparison of the spectra of the hyperporphyrin spectral complexes titrated with various types of alcohol and imidazole, with the spectrum of Co-P450 cam in the oxidized state support the idea that an axial thiolate at the fifth position and a hydroxyl group of alcohol at the sixth position of the heme form the coordination site of Co-P450 cam The CoPPIX-thiolate-ethanol complex retaining S −-Co(III)-OH coordination is thought to be a possible model of Co-P450 cam in the oxidized state.
Published Version
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