Sep 27, 1983

Cytochrome P-450 isozyme 1 from phenobarbital-induced rat liver: purification, characterization, and interactions with metyrapone and cytochrome b5

D J Waxman, C Walsh


Cytochrome P-450 isozyme 1 (PB-1) (Mr congruent to 53 000) was purified to apparent homogeneity from phenobarbital (PB)-induced rat liver microsomes, and its spectral, structural, immunochemical, and catalytic properties were determined. PB-1, present in significant amounts in uninduced rat liver microsomes, is induced approximately 2-4-fold by phenobarbital, as compared to the greater than 30-fold induction typical of the major PB isozymes characterized previously. PB-1 was distinguished from the major PB-induced isozymes PB-4 and PB-5 [Waxman, D. J., & Walsh, C. (1982) J. Biol. Chem. 257, 10446-10457] by the absence of a Fe2+-metyrapone P446 complex, by its unique NH2-terminal sequence and distinct peptide maps, by the lack of immuno-cross-reactivity to PB-4, and by its characteristic substrate-specificity profile. Metyrapone effected a saturable enhancement of several PB-1-catalyzed reactions in the reconstituted system [Km(metyrapone) congruent to 200 microM], which varied in magnitude with the substrate, with a maximal stimulation of 5-8-fold in the case of acetanilide 4-hydroxylation. That metyrapone enhanced the corresponding microsomal activities only in cases where the metyrapone-sensitive PB-4 did not catalyze the sam...Continue Reading

Mentioned in this Paper

Tissue Membrane
SU 4885
August Rats
Cytochrome P450
Electron Transport
Cytochrome P-450 Oxygenase
Proteolytic Enzyme
Microsomes, Liver

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