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Gene Review

Cyb5a  -  cytochrome b5 type A (microsomal)

Rattus norvegicus

Synonyms: Cyb5, Cytochrome b5
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Disease relevance of Cyb5


High impact information on Cyb5

  • Both proteins exist as dimeric molecules with one molybdenum and one cytochrome b5-type heme per sub-unit [4].
  • Cytochrome P450 heme degradation was then determined directly by injecting radiolabeled delta-aminolevulinic acid and measuring radioactivity in CO-binding particles (microsomes incubated with protease to remove cytochrome b5) prepared at various times thereafter [5].
  • In liver of rats with portal vein ligation, microsomal cytochrome P450 levels were significantly less than in sham-operated control rats, but cytochrome b5, NADPH-cytochrome c reductase, and glucose-6-phosphatase were unaltered [6].
  • In rats fed commercial chow diet, cytochrome P-450 content and drug-metabolizing enzyme activity in villous tip cells of duodenal mucosa were higher than in animals fed a semisynthetic diet, but cytochrome b5 and NADPH-cytochrome P-450 reductase were unaffected [7].
  • The carboxy-terminal 10 amino acid residues of cytochrome b5 are necessary for its targeting to the endoplasmic reticulum [8].

Chemical compound and disease context of Cyb5


Biological context of Cyb5


Anatomical context of Cyb5


Associations of Cyb5 with chemical compounds

  • The typical HPGG motif of the cytochrome b5-like domain, and particularly histidine in this motif, is required for the activity of the enzyme, whatever the substrate [19].
  • The non-conservative substitutions are located at the surface of the known three-dimensional structure of calf microsomal cytochrome b5 except for the substitution of histidine-15 by arginine [20].
  • The blocked amino terminus of cytochrome b5 was identified as N-acetylalanine [14].
  • Isolation of this species of cytochrome b5 in its native form from microsomes by means of detergent solubilization required the inclusion of the protease inhibitor, phenylmethylsulfonyl fluoride, throughout the isolation steps [14].
  • However, the Golgi enzyme was unstable inasmuch as pelleting and resuspending the fresh fractions resulted in a considerable inactivation (40--60%), which was further increased with subsequent storage at 4 degrees C. A similar inactivation was observed using cytochrome b5 but not ferricyanide as electron acceptor [21].

Physical interactions of Cyb5


Enzymatic interactions of Cyb5


Regulatory relationships of Cyb5


Other interactions of Cyb5


Analytical, diagnostic and therapeutic context of Cyb5


  1. Stearoyl-coenzyme A desaturase activity in Novikoff hepatoma. Prasad, M.R., Joshi, V.C. Lipids (1979) [Pubmed]
  2. Acridine orange-mediated photodamage of microsomal- and lysosomal fractions. Olsson, G.M., Brunmark, A., Brunk, U.T. Virchows Arch., B, Cell Pathol. (1989) [Pubmed]
  3. Effect of extra-hepatic Walker sarcoma 256 on the synthesis and degradation of liver cytochromes P-450 and b5. Raw, I. Braz. J. Med. Biol. Res. (1983) [Pubmed]
  4. Purification and properties of sulfite oxidase from human liver. Johnson, J.L., Rajagopalan, K.V. J. Clin. Invest. (1976) [Pubmed]
  5. Hepatic heme metabolism and cytochrome P450 in cirrhotic rat liver. Farrell, G.C., Zaluzny, L. Gastroenterology (1985) [Pubmed]
  6. Portal vein ligation selectively lowers hepatic cytochrome P450 levels in rats. Farrell, G.C., Zaluzny, L. Gastroenterology (1983) [Pubmed]
  7. Oxidative metabolism of foreign compounds in rat small intestine: cellular localization and dependence on dietary iron. Hoensch, H., Woo, C.H., Raffin, S.B., Schmid, R. Gastroenterology (1976) [Pubmed]
  8. The carboxy-terminal 10 amino acid residues of cytochrome b5 are necessary for its targeting to the endoplasmic reticulum. Mitoma, J., Ito, A. EMBO J. (1992) [Pubmed]
  9. Effects of hepatic ischemia-reperfusion injury on the hepatic mixed function oxidase system in rats. Lindstrom, T.D., Hanssen, B.R., Bendele, A.M. Mol. Pharmacol. (1990) [Pubmed]
  10. Genetic analysis of cytochrome b5 from arachidonic acid-producing fungus, Mortierella alpina 1S-4: cloning, RNA editing and expression of the gene in Escherichia coli, and purification and characterization of the gene product. Kobayashi, M., Sakuradani, E., Shimizu, S. J. Biochem. (1999) [Pubmed]
  11. Antitumor agents. I. Effect of 5-fluorouracil and cyclophosphamide on liver microsomes and thymus of rat. Ogiso, T., Noda, N., Asai, N., Kato, Y. Jpn. J. Pharmacol. (1976) [Pubmed]
  12. Induction of drug metabolizing enzymes in the liver of rats infested with Fasciola hepatica. Galtier, P., Larrieu, G., Lesca, P. J. Pharm. Pharmacol. (1985) [Pubmed]
  13. The reducing ability of iron chelates by NADH-cytochrome B5 reductase or cytochrome B5 responsible for NADH-supported lipid peroxidation. Miura, A., Tampo, Y., Yonaha, M. Biochem. Mol. Biol. Int. (1995) [Pubmed]
  14. Chemical structure of rat liver cytochrome b5. Isolation of peptides by high-pressure liquid chromatography. Ozols, J., Heinemann, F.S. Biochim. Biophys. Acta (1982) [Pubmed]
  15. Mechanism of rat liver microsomal stearyl-CoA desaturase. Studies of the substrate specificity, enzyme-substrate interactions, and the function of lipid. Enoch, H.G., Catalá, A., Strittmatter, P. J. Biol. Chem. (1976) [Pubmed]
  16. An oxygraphic method for the determination of cholesterol and measurement of the slow oxygen-consuming reactions of hepatic microsomes. Miyake, Y., Fukuyama, M. J. Biochem. (1976) [Pubmed]
  17. The binding of cytochrome b5 to plasma membranes of rat liver: its implication for membrane specificity and biogenesis. Remacle, J. Biochim. Biophys. Acta (1980) [Pubmed]
  18. Identification of outer mitochondrial membrane cytochrome b5 as a modulator for androgen synthesis in Leydig cells. Ogishima, T., Kinoshita, J.Y., Mitani, F., Suematsu, M., Ito, A. J. Biol. Chem. (2003) [Pubmed]
  19. Distinct roles of endoplasmic reticulum cytochrome b5 and fused cytochrome b5-like domain for rat Delta6-desaturase activity. Guillou, H., D'Andrea, S., Rioux, V., Barnouin, R., Dalaine, S., Pedrono, F., Jan, S., Legrand, P. J. Lipid Res. (2004) [Pubmed]
  20. Two homologous cytochromes b5 in a single cell. Lederer, F., Ghrir, R., Guiard, B., Cortial, S., Ito, A. Eur. J. Biochem. (1983) [Pubmed]
  21. Localization and biosynthesis of NADH-cytochrome b5 reductase, an integral membrane protein, in rat liver cells. I. Distribution of the enzyme activity in microsomes, mitochondria, and golgi complex. Borgese, N., Meldolesi, J. J. Cell Biol. (1980) [Pubmed]
  22. Cytochrome b5/cytochrome b5 reductase complex in rat liver microsomes has NADH-linked aquacobalamin reductase activity. Watanabe, F., Nakano, Y., Saido, H., Tamura, Y., Yamanaka, H. J. Nutr. (1992) [Pubmed]
  23. An enzymatically active chimeric protein containing the hydrophilic form of NADPH-cytochrome P450 reductase fused to the membrane-binding domain of cytochrome b5. Gilep, A.A., Guryev, O.L., Usanov, S.A., Estabrook, R.W. Biochem. Biophys. Res. Commun. (2001) [Pubmed]
  24. The roles of cytochrome b5 in reconstituted monooxygenase systems containing various forms of hepatic microsomal cytochrome P-450. Imai, Y. J. Biochem. (1981) [Pubmed]
  25. Involvement of cytochrome b5 in the metabolism of tetrachlorobiphenyls catalyzed by CYP2B1 and CYP1A1. Matsusue, K., Ariyoshi, N., Oguri, K., Koga, N., Yoshimura, H. Chemosphere (1996) [Pubmed]
  26. Propylthiouracil, a selective inhibitor of NADH-cytochrome b5 reductase. Lee, E., Kariya, K. FEBS Lett. (1986) [Pubmed]
  27. Effect of drugs and hormones on rat liver dimethylaminoazobenzene reductase activity. de-Araujo, P.S., de-Andrade-Silva, E., Raw, I. Braz. J. Med. Biol. Res. (1982) [Pubmed]
  28. NADPH-flavodoxin reductase and flavodoxin from Escherichia coli: characteristics as a soluble microsomal P450 reductase. Jenkins, C.M., Waterman, M.R. Biochemistry (1998) [Pubmed]
  29. Role of cytochrome b5 in NADH-dependent microsomal reduction of ferric complexes, lipid peroxidation, and hydrogen peroxide generation. Yang, M.X., Cederbaum, A.I. Arch. Biochem. Biophys. (1995) [Pubmed]
  30. Cytochrome b5-like hemoprotein of outer mitochondrial membrane: OM cytochrome b. II. Contribution of OM cytochrome b to rotenone-insensitive NADH-cytochrome c reductase activity. Ito, A. J. Biochem. (1980) [Pubmed]
  31. Rate of alteration of hepatic mixed-function oxidase system in rats fed different dietary fats. Ammouche, A., Dinh, L., Youyou, A., Clément, M., Bourre, J.M. Biochem. Cell Biol. (1993) [Pubmed]
  32. Subfractionation of rat liver microsomes by immunoprecipitation and immunoadsorption methods. Kawajiri, K., Ito, A., Omura, T. J. Biochem. (1977) [Pubmed]
  33. Evidence against cytochrome b5 involvement in liver microsomal fatty acid elongation. Demirkapi, N., Carreau, J.P., Ghesquier, D. Biochim. Biophys. Acta (1991) [Pubmed]
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