Inhibition of microsomal drug metabolism by mitochondria and cytochrome c oxidation of extramitochondrial NADPH. 1982

K Tihanyi, and K Mészáros, and I Horváth

Microsomal aniline p-hydroxylase and aminopyrine N-demethylase activities were inhibited by mitochondria. The magnitude of the inhibition increased in parallel with the amount of added mitochondria. The inhibition was reverted by 0.2 mM KCN. Marked inhibition of these microsomal enzyme activities was observed also in the presence of cytochrome c and low amounts of mitochondria causing negligible inhibition in themselves. The inhibition increased with the concentration of cytochrome c and it was reverted by KCN. Microsome-free mitochondria did not oxidize NADPH even in the presence of cytochrome c, although NADH oxidation has been demonstrated under these circumstances [Sottocasa et al., J. cell Biol. 32, 415, (1967)]. However, completion of the system by addition of microsomes resulted in the oxidation of NADPH, which was inhibited by KCN. These findings may indicate the cooperation of the microsomal and mitochondrial compartments in the regulation of drug metabolism.

UI MeSH Term Description Entries
D008862 Microsomes, Liver Closed vesicles of fragmented endoplasmic reticulum created when liver cells or tissue are disrupted by homogenization. They may be smooth or rough. Liver Microsomes,Liver Microsome,Microsome, Liver
D008930 Mitochondria, Liver Mitochondria in hepatocytes. As in all mitochondria, there are an outer membrane and an inner membrane, together creating two separate mitochondrial compartments: the internal matrix space and a much narrower intermembrane space. In the liver mitochondrion, an estimated 67% of the total mitochondrial proteins is located in the matrix. (From Alberts et al., Molecular Biology of the Cell, 2d ed, p343-4) Liver Mitochondria,Liver Mitochondrion,Mitochondrion, Liver
D009249 NADP Nicotinamide adenine dinucleotide phosphate. A coenzyme composed of ribosylnicotinamide 5'-phosphate (NMN) coupled by pyrophosphate linkage to the 5'-phosphate adenosine 2',5'-bisphosphate. It serves as an electron carrier in a number of reactions, being alternately oxidized (NADP+) and reduced (NADPH). (Dorland, 27th ed) Coenzyme II,Nicotinamide-Adenine Dinucleotide Phosphate,Triphosphopyridine Nucleotide,NADPH,Dinucleotide Phosphate, Nicotinamide-Adenine,Nicotinamide Adenine Dinucleotide Phosphate,Nucleotide, Triphosphopyridine,Phosphate, Nicotinamide-Adenine Dinucleotide
D010084 Oxidation-Reduction A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471). Redox,Oxidation Reduction
D011919 Rats, Inbred Strains Genetically identical individuals developed from brother and sister matings which have been carried out for twenty or more generations or by parent x offspring matings carried out with certain restrictions. This also includes animals with a long history of closed colony breeding. August Rats,Inbred Rat Strains,Inbred Strain of Rat,Inbred Strain of Rats,Inbred Strains of Rats,Rat, Inbred Strain,August Rat,Inbred Rat Strain,Inbred Strain Rat,Inbred Strain Rats,Inbred Strains Rat,Inbred Strains Rats,Rat Inbred Strain,Rat Inbred Strains,Rat Strain, Inbred,Rat Strains, Inbred,Rat, August,Rat, Inbred Strains,Rats Inbred Strain,Rats Inbred Strains,Rats, August,Rats, Inbred Strain,Strain Rat, Inbred,Strain Rats, Inbred,Strain, Inbred Rat,Strains, Inbred Rat
D003574 Cytochrome c Group A group of cytochromes with covalent thioether linkages between either or both of the vinyl side chains of protoheme and the protein. (Enzyme Nomenclature, 1992, p539) Cytochromes Type c,Group, Cytochrome c,Type c, Cytochromes
D004364 Pharmaceutical Preparations Drugs intended for human or veterinary use, presented in their finished dosage form. Included here are materials used in the preparation and/or formulation of the finished dosage form. Drug,Drugs,Pharmaceutical,Pharmaceutical Preparation,Pharmaceutical Product,Pharmaceutic Preparations,Pharmaceutical Products,Pharmaceuticals,Preparations, Pharmaceutical,Preparation, Pharmaceutical,Preparations, Pharmaceutic,Product, Pharmaceutical,Products, Pharmaceutical
D000633 Aminopyrine N-Demethylase Aminopyrine N Demethylase,Demethylase, Aminopyrine N,N Demethylase, Aminopyrine,N-Demethylase, Aminopyrine
D000815 Aniline Hydroxylase A drug-metabolizing, cytochrome P-450 enzyme which catalyzes the hydroxylation of aniline to hydroxyaniline in the presence of reduced flavoprotein and molecular oxygen. EC 1.14.14.-. Hydroxylase, Aniline
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia

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