The formation of g=2.49-species of cytochrome P450 in the rat liver by PCB126 oral administration: identification of heme axial ligands by EPR spectroscopy |
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Authors: | Morita Hidetoshi Yoshikawa Hiroshi Takizawa Tatsuya Shirai Mitsuyuki Akahori Fumiaki Yoshimura Tetsuhiko |
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Institution: | School of Veterinary Medicine, Azabu University, Sagamihara. morita@azabu-u.ac.jp |
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Abstract: | Rat livers and microsomes were subjected to electron paramagnetic resonance (EPR) measurements at 77 K. The EPR spectra of the livers from the control group, carbon tetrachloride-, 3-methylcholanthrene-, and 3,3',4,4',5-pentachlorobiphenyl (PCB126)-treated rats exhibited an EPR spectrum at g=2.40, 2.24, and 1.93, which is characteristic of P450 in a resting state. The liver of the PCB126-treated rats showed an additional distinct EPR spectrum at g=2.49, 2.26, and 1.87 (g=2.49-species). The heme environmental structure of g=2.49-species was identified by crystal field analysis using three EPR g-values of the microsome treated with various chemicals. These results indicated that g=2.49-species is a hemeprotein with cysteine thiolate at the 5th coordination site, and a nitrogenous ligand at the 6th site. |
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