A Model of Cytochrome P-450 : Optical and EPR Properties of a Thiol-containing Peptide-Hemin System and Its Activity of Aniline Hydroxylation

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The model system consisting of α-mercaptopropionylglycine (α-MPG), hemin and pyridine exhibited similar absorption and electron paramagnetic resonance spectra to cytochrome P-450. In the presence of an excess amount of pyridine, a low-spin state of heme iron was observed at both 293 and 77°K. A transition of the high-spin state of Fe (III) at 293°K to the low-spin state was detected at 77°K in the presence of trace amount of pyridine. When pyridine was omitted from the system, the high-spin state was produced. Under exposure of CO of this model system, the characteristic absorption band of 450 nm was observed, which is typical with cytochrome P-450. Two types of spectral change were obtained when aminopyrine (type I) or aniline (type II) was added to α-MPG-hemin. Spectral dissociation constant K_s of aniline with model system was compared with the reported value with a biological system. It was also discussed that the hydroxylating ability with model and liver microsomal systems.
公益社団法人日本薬学会の論文
1978-05-25