Open AccessOxidation of Cytochrome b 5 by Hydroperoxides in Rat Liver
Author(s) -
SIES Helmut,
GROSSKOPF Max
Publication year - 1975
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1975.tb02326.x
Subject(s) - cytochrome b5 , cytochrome , chemistry , cumene hydroperoxide , hemeprotein , cytochrome c , cytochrome b , biochemistry , cytochrome c1 , cytochrome c peroxidase , coenzyme q – cytochrome c reductase , redox , cytochrome p450 reductase , cytochrome c oxidase , heme , photochemistry , mitochondrion , organic chemistry , enzyme , mitochondrial dna , catalysis , gene
1 Spectral changes following the addition of hydroperoxides to isolated hepatocytes and to perfused rat liver were observed. Cytochrome b 5 is the major, if not the only, hemoprotein exhibiting redox changes under these conditions: cytochrome b 5 is oxidized by added hydroperoxides, e.g. tert ‐butyl or cumene hydroperoxides. No spectral changes attributable to cytochrome b 5 were observed with tert ‐butanol. 2 The effect is present also when the mitochondrial respiratory chain is inhibited by antimycin A, and it is not observable with isolated mitochondria. On the other hand, the oxidation of cytochrome b 5 by hydroperoxides is readily demonstrable in microsomal fractions in presence of NADH. 3 Spectral evidence for a participation of the other microsomal hemoprotein, cytochrome P ‐450, in the hydroperoxide‐linked effects was not obtained. Thus, in hepatocytes from phenobarbital‐pretreated rats, no formation of cytochrome P ‐420, no displacement of a type I substrate, hexobarbital, and no major steady state redox change of cytochrome P ‐450 was detectable. However, when cytochrome P ‐450 was dithionite‐reduced, an oxidation of this cytochrome occurred upon subsequent hydroperoxide addition. 4 Hydrogen peroxide addition to hepatocytes also leads to a lower steady‐state degree of reduction of cytochrome b 5 . Evidence is provided with hepatocytes from rats pretreated with 3‐amino‐1,2,4‐triazole that H 2 O 2 generated intracellularly, e.g. from added glycolate, also causes a detectable oxidation of cytochrome b 5 . 5 The mechanism of these hydroperoxide effects remains to be established, and it is not clear whether cytochrome b 5 reacts directly or indirectly. However, it is suggested that these effects may be of significance for the further study of cytochrome‐ b 5 ‐linked metabolic pathways.