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CytochromeP-450 ligands: Metyrapone revisited

Authors
Journal
Archives of Biochemistry and Biophysics
0003-9861
Publisher
Elsevier
Publication Date
Volume
241
Issue
2
Identifiers
DOI: 10.1016/0003-9861(85)90562-4
Keywords
  • Oxygenases
  • Microsomes
  • And P-450 Reactions

Abstract

Abstract Expressing metyrapone interactions with ferrous cytochrome P-450 as ligand saturation by cytochrome, rather than the more conventional cytochrome saturation by ligand, an extinction coefficient of 68.5 ± 1.8 m m −1 cm −1 for the metyrapone complex of dithionite-reduced rat hepatic microsomal cytochrome P-450 was derived. Utilizing this new extinction coefficient, the increased cytochrome P-450 present after phenobarbital induction was almost exclusively that which is able to both bind to metyrapone and form a metabolic-intermediate complex from norbenzphetamine. However, it was not the only subpopulation present in microsomes that was able to bind metyrapone, nor the only one capable of forming a metabolic intermediate complex from norbenzphetamine. Thus, neither technique alone can be used to quantitate the “phenobarbital-induced form” of cytochrome P-450.

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