The Binding of Trichlorofluoromethane and other Haloalkanes to Cytochrome P-450 under Aerobic and Anaerobic Conditions

Abstract

1. Trichlorofluoromethane and other haloalkanes interact with hepatic microsomal cytochrome P-450 to give type I spectra under aerobic conditions.

2. Anaerobically, CCl₃F, CCl₂F. CClF₂ and CCl₄ interact to give peaks at approx. 420 nm and 455 nm; the other haloalkanes gave peaks at approx. 420 nm only. The formation of the 452 nm peak for CCl₃F was time-dependent, and dependent on substrate concentration.

3. Iso-octane extraction of the microsomal preparation increased the magnitude of spectral interaction under reducing conditions but not its rate of formation. Phenobarbitone pretreatment increased the magnitude of the spectral interaction; 3-methylcholanthrene pre-treatment had no effect on the magnitude of the 452 nm peak but decreased its rate of formation.

4. It is suggested that the 452 nm peak represents the interaction of a reactive species formed from CCl₃F with the Fe²⁺ of the haem of reduced cytochrome P-450.