Biomaterial Database

Induction and purification of cytochrome P450 1A1 from 3-methylcholanthrene-treated tilapia, Oreochromis niloticus x Oreochromis aureus. 1995

Y F Ueng, and T H Ueng

Institute of Toxicology, College of Medicine, National Taiwan University, Taipei, Republic of China.

Pretreatments of freshwater fish tilapia, Oreochromis niloticus x O. aureus, with 3-methylcholanthrene (3-MC) and polychlorinated biphenyls (PCBs) increased liver microsomal cytochromes P450 (P450) and b5 contents, benzo[a]pyrene hydroxylation, and 7-ethoxyresorufin and 7-ethoxycoumarin O-dealkylations. The pretreatments also increased gill microsomal benzo[a]pyrene and 7-ethoxyresorufin oxidations. Immunoblot analysis of liver and gill microsomes revealed that 3-MC and PCBs induced a protein recognized by the mouse monoclonal antibody (MAb) 1-12-3 against scup P450 1A1. Northern analysis of liver and gill RNA showed that 3-MC and PCBs increased the intensity of 2.9-kb- and 1.5-kb-sized mRNA bands hybridizable to a trout P450 1A1 cDNA probe. Pretreatment with phenobarbital was without effects on the monooxygenase activity or protein or mRNA levels in liver and gill. A 3-MC-inducible P450 hemoprotein (M(r) = 59,000) and a NADPH-cytochrome P450 reductase flavoprotein (M(r) = 74,000) were purified from liver microsomes. The tilapia P450 hemoprotein showed an absorption maximum at 447 nm in CO-difference spectrum and a strong immunoreactivity with MAb 1-12-3. A reconstituted tilapia monooxygenase system consisting of P450 and NADPH-cytochrome P450 reductase was effective in the catalysis of 7-ethoxyresorufin, benzo[a]pyrene, and 7-ethoxycoumarin oxidations, but not in N-nitrosodimethylamine demethylation. These results show that 3-MC and PCBs can induce P450 1A1 in tilapia liver and gill and the tilapia P450 is highly similar to other teleost P450 1A1 with respect to spectral, immunochemical, and catalytic properties.

UI	MeSH Term	Description	Entries
D008099	Liver	A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances.	Livers
D008297	Male		Males
D008748	Methylcholanthrene	A carcinogen that is often used in experimental cancer studies.	20-Methylcholanthrene,3-Methylcholanthrene,20 Methylcholanthrene,3 Methylcholanthrene
D008861	Microsomes	Artifactual vesicles formed from the endoplasmic reticulum when cells are disrupted. They are isolated by differential centrifugation and are composed of three structural features: rough vesicles, smooth vesicles, and ribosomes. Numerous enzyme activities are associated with the microsomal fraction. (Glick, Glossary of Biochemistry and Molecular Biology, 1990; from Rieger et al., Glossary of Genetics: Classical and Molecular, 5th ed)	Microsome
D008969	Molecular Sequence Data	Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.	Sequence Data, Molecular,Molecular Sequencing Data,Data, Molecular Sequence,Data, Molecular Sequencing,Sequencing Data, Molecular
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
D010088	Oxidoreductases	The class of all enzymes catalyzing oxidoreduction reactions. The substrate that is oxidized is regarded as a hydrogen donor. The systematic name is based on donor:acceptor oxidoreductase. The recommended name will be dehydrogenase, wherever this is possible; as an alternative, reductase can be used. Oxidase is only used in cases where O2 is the acceptor. (Enzyme Nomenclature, 1992, p9)	Dehydrogenases,Oxidases,Oxidoreductase,Reductases,Dehydrogenase,Oxidase,Reductase
D010105	Oxygenases	Oxidases that specifically introduce DIOXYGEN-derived oxygen atoms into a variety of organic molecules.	Oxygenase
D011078	Polychlorinated Biphenyls	Industrial products consisting of a mixture of chlorinated biphenyl congeners and isomers. These compounds are highly lipophilic and tend to accumulate in fat stores of animals. Many of these compounds are considered toxic and potential environmental pollutants.	PCBs,Polychlorinated Biphenyl,Polychlorobiphenyl Compounds,Biphenyl, Polychlorinated,Biphenyls, Polychlorinated,Compounds, Polychlorobiphenyl
D002273	Carcinogens	Substances that increase the risk of NEOPLASMS in humans or animals. Both genotoxic chemicals, which affect DNA directly, and nongenotoxic chemicals, which induce neoplasms by other mechanism, are included.	Carcinogen,Oncogen,Oncogens,Tumor Initiator,Tumor Initiators,Tumor Promoter,Tumor Promoters,Initiator, Tumor,Initiators, Tumor,Promoter, Tumor,Promoters, Tumor