Biomaterial Database

Evidence for a predominantly NADH-dependent O-dealkylating system in rat hepatic microsomes. 1985

S Kuwahara, and G J Mannering

This study compared the NADH- and NADPH-supported p-nitrophenetole (NP) O-deethylase, ethylmorphine (EM) O-deethylase and EM N-demethylase activities of rat hepatic microsomes with respect to dioxygen requirement, inhibition by carbon monoxide, inhibition by classical inhibitors of cytochrome P-450 systems, and the involvement of NADH-cytochrome b5, cytochrome b5 reductase and NADPH-cytochrome P-450 reductase. The results generated the following conclusions and speculations: NADH- and NADPH-supported O-deethylations of NP involve different P-450 hemoproteins. This conclusion was based largely on the observations that the NADPH-supported reaction was inhibited by carbon monoxide and cyanide (5 mM), whereas the NADH-supported reaction was not; the NADH-supported reaction required a relatively high pO2 for maximal activity, whereas the NADPH-supported reaction did not, and the NADPH-supported reaction was depressed in microsomes from rats that had been administered Co2+, Mn2+, allylisopropylacetamide (AIA) or polyriboinosinic acid X polyribocytidylic acid (poly IC), whereas the NADH-supported reaction was not. However, the NADH- and NADPH-supported reactions shared some common features: both were strongly inhibited by alpha-naphthoflavone and weakly inhibited by 2-diethylaminoethyl 2,2-diphenyl valerate HCI (SKF 525-A), both were destroyed by linoleic acid hydroperoxide, and both were induced by 3-methylcholanthrene (MC) and phenobarbital. The use of antibodies against NADPH-cytochrome P-450 reductase, NADH-cytochrome b5 reductase and cytochrome b5 demonstrated that both the NADH- and the NADPH-supported reactions depend on established components of cytochrome P-450 systems. The P-450 hemoproteins involved primarily in both the NADH- and NADPH-supported deethylation of NP are the P1-450 type, i.e. they are markedly induced by MC and inhibited by alpha-napthoflavone. The NADH- and NADPH-supported O-deethylations of NP involve separate electron transfer systems.(ABSTRACT TRUNCATED AT 400 WORDS)

UI	MeSH Term	Description	Entries
D008041	Linoleic Acids	Eighteen-carbon essential fatty acids that contain two double bonds.	Acids, Linoleic
D008054	Lipid Peroxides	Peroxides produced in the presence of a free radical by the oxidation of unsaturated fatty acids in the cell in the presence of molecular oxygen. The formation of lipid peroxides results in the destruction of the original lipid leading to the loss of integrity of the membranes. They therefore cause a variety of toxic effects in vivo and their formation is considered a pathological process in biological systems. Their formation can be inhibited by antioxidants, such as vitamin E, structural separation or low oxygen tension.	Fatty Acid Hydroperoxide,Lipid Peroxide,Lipoperoxide,Fatty Acid Hydroperoxides,Lipid Hydroperoxide,Lipoperoxides,Acid Hydroperoxide, Fatty,Acid Hydroperoxides, Fatty,Hydroperoxide, Fatty Acid,Hydroperoxide, Lipid,Hydroperoxides, Fatty Acid,Peroxide, Lipid,Peroxides, Lipid
D008297	Male		Males
D008345	Manganese	A trace element with atomic symbol Mn, atomic number 25, and atomic weight 54.94. It is concentrated in cell mitochondria, mostly in the pituitary gland, liver, pancreas, kidney, and bone, influences the synthesis of mucopolysaccharides, stimulates hepatic synthesis of cholesterol and fatty acids, and is a cofactor in many enzymes, including arginase and alkaline phosphatase in the liver. (From AMA Drug Evaluations Annual 1992, p2035)
D008748	Methylcholanthrene	A carcinogen that is often used in experimental cancer studies.	20-Methylcholanthrene,3-Methylcholanthrene,20 Methylcholanthrene,3 Methylcholanthrene
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
D009243	NAD	A coenzyme composed of ribosylnicotinamide 5'-diphosphate coupled to adenosine 5'-phosphate by pyrophosphate linkage. It is found widely in nature and is involved in numerous enzymatic reactions in which it serves as an electron carrier by being alternately oxidized (NAD+) and reduced (NADH). (Dorland, 27th ed)	Coenzyme I,DPN,Diphosphopyridine Nucleotide,Nadide,Nicotinamide-Adenine Dinucleotide,Dihydronicotinamide Adenine Dinucleotide,NADH,Adenine Dinucleotide, Dihydronicotinamide,Dinucleotide, Dihydronicotinamide Adenine,Dinucleotide, Nicotinamide-Adenine,Nicotinamide Adenine Dinucleotide,Nucleotide, Diphosphopyridine
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
D009251	NADPH-Ferrihemoprotein Reductase	A flavoprotein that catalyzes the reduction of heme-thiolate-dependent monooxygenases and is part of the microsomal hydroxylating system. EC 1.6.2.4.	Cytochrome P-450 Reductase,Ferrihemoprotein P-450 Reductase,NADPH Cytochrome P-450 Oxidoreductase,NADPH Cytochrome P-450 Reductase,NADPH Cytochrome c Reductase,Cytochrome P-450 Oxidase,Cytochrome P450 Reductase,Ferrihemoprotein P450 Reductase,NADPH Cytochrome P450 Oxidoreductase,NADPH Cytochrome P450 Reductase,NADPH-Cytochrome P450 Reductase,NADPH-P450 Reductase,Cytochrome P 450 Oxidase,Cytochrome P 450 Reductase,Ferrihemoprotein P 450 Reductase,NADPH Cytochrome P 450 Oxidoreductase,NADPH Cytochrome P 450 Reductase,NADPH Ferrihemoprotein Reductase,NADPH P450 Reductase,Oxidase, Cytochrome P-450,P-450 Oxidase, Cytochrome,P450 Reductase, Cytochrome,P450 Reductase, NADPH-Cytochrome,Reductase, Cytochrome P-450,Reductase, Cytochrome P450,Reductase, Ferrihemoprotein P-450,Reductase, Ferrihemoprotein P450,Reductase, NADPH-Cytochrome P450,Reductase, NADPH-Ferrihemoprotein,Reductase, NADPH-P450
D009578	Nitrobenzenes	BENZENE derivatives carrying nitro group substituents.