The peroxidatic function of liver microsomal cytochrome P-450: Comparison of hydrogen peroxide and NADPH-catalysed iV-demethylation reactions

R. W. Estabrook Department of Biochemistry, University of Texas Health Science Center, Dallas, TX, 75235, USA

C. Martin-wixtrom Department of Biochemistry, University of Texas Health Science Center, Dallas, TX, 75235, USA

Y. Saeki Department of Biochemistry, University of Texas Health Science Center, Dallas, TX, 75235, USA; Central Research Laboratory, Shiga University of Medical Science, Seta, Ohtsu, Shiga, 520-21, Japan

R. Renneberg Department of Biochemistry, University of Texas Health Science Center, Dallas, TX, 75235, USA; Central Institute of Molecular Biology, Academy of Sciences of GDR, Department of Applied Enzymology, GDR-1115 Berlin-Buch, Robert-Rossle-Str. 10DR, Germany

A. Hildebrandt Department of Biochemistry, University of Texas Health Science Center, Dallas, TX, 75235, USA; Max von Pettenkofer Institut, Bundes Gesundheitsamt, Postfache 330013, D-1000, Berlin 33, FR Germany

J. Werringloer Department of Biochemistry, University of Texas Health Science Center, Dallas, TX, 75235, USA; Department of Toxicology, University of Tübingen, Lothar Meyer-Bau Wilhelmstrasse 56, D-7400, Tübingen 1, FR Germany

Abstract

1. Fifteen different secondary and tertiary methyl amines have been examined as substrates for the cytochromes P-450 of rat-liver microsomes to determine the similarities or differences between the NADPH and oxygen-dependent N-demethylation reaction and the reaction occurring in the presence of hydrogen peroxide. No apparent correlation of the rates of formaldehyde formation using the two different conditions of oxidation was observed.

2. The types of cytochromes P-450 were altered by using rat-liver microsomes from animals treated with various inducing agents. No obvious predictable dependence on the type of cytochrome P-450 present was obtained for the hydrogen peroxide-supported peroxidatic reaction.

3. It is concluded that the hydrogen peroxide-dependent JV-demethylation reaction occurs by a reaction mechanism distinct from that occurring during the mixed-function oxidase activity of cytochrome P-450 obtained in the presence of NADPH and oxygen.

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The peroxidatic function of liver microsomal cytochrome P-450: Comparison of hydrogen peroxide and NADPH-catalysed iV-demethylation reactions

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The peroxidatic function of liver microsomal cytochrome P-450: Comparison of hydrogen peroxide and NADPH-catalysed iV-demethylation reactions

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