The world's first wiki where authorship really matters (Nature Genetics, 2008). Due credit and reputation for authors. Imagine a global collaborative knowledge base for original thoughts. Search thousands of articles and collaborate with scientists around the globe.

wikigene or wiki gene protein drug chemical gene disease author authorship tracking collaborative publishing evolutionary knowledge reputation system wiki2.0 global collaboration genes proteins drugs chemicals diseases compound
Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)



Gene Review

CYB5A  -  cytochrome b5 type A (microsomal)

Homo sapiens

Synonyms: CYB5, Cytochrome b5, MCB5, Microsomal cytochrome b5 type A
Welcome! If you are familiar with the subject of this article, you can contribute to this open access knowledge base by deleting incorrect information, restructuring or completely rewriting any text. Read more.

Disease relevance of CYB5A


Psychiatry related information on CYB5A


High impact information on CYB5A


Chemical compound and disease context of CYB5A


Biological context of CYB5A


Anatomical context of CYB5A


Associations of CYB5A with chemical compounds

  • Regulation of 17,20 lyase activity by cytochrome b5 and by serine phosphorylation of P450c17 [15].
  • These residues are invoked to mediate protein-protein interaction between cytochrome b5 and CYP17, which 'awakens' the lyase activity of the enzyme required for androgen formation [21].
  • It was found that the mutation of Lys83, Arg347 and Arg358 produced proteins that were deficient in their responsiveness to cytochrome b5, and the effect was most pronounced for the two arginine mutants (Arg347-->His and Arg358-->Gln) which have been found in male patients suffering from genital ambiguity [21].
  • It is specific for NADH and reduces artificial substrates such as dichlorophenol and tetrazolium derivatives, but not natural substrates such as methemoglobin, cytochrome b5 or lipoate [22].
  • The purified enzyme was characterized by a high specificity for NADH as electron donor (Km = 6.4 mumol/L v Km greater than 1.6 mmol/L for NADPH) and exhibited a maximal turnover of ca. 30,000 min-1 at 22 degrees C with either ferricyanide or cytochrome b5 (Km = 10 nmol/L) as electron acceptor [23].

Physical interactions of CYB5A


Enzymatic interactions of CYB5A

  • Like the pig CYP17, the human CYP17 also catalysed the cytochrome b5-dependent direct cleavage of pregnenolone into the delta 5,16-steroid, but unlike it the human enzyme did not cleave progesterone at all [2].
  • In recombinant CYP from human B-lymphoblast cells or baculovirus-infected insect cells and in reconstituted systems, a requirement of cytochrome b5 (b5) for POD activities catalysed by CYP2E1 and CYP3A4 was observed [27].

Regulatory relationships of CYB5A


Other interactions of CYB5A


Analytical, diagnostic and therapeutic context of CYB5A


  1. Congenital methemoglobinemia with a deficiency of cytochrome b5. Hegesh, E., Hegesh, J., Kaftory, A. N. Engl. J. Med. (1986) [Pubmed]
  2. Modulation of the activity of human 17 alpha-hydroxylase-17,20-lyase (CYP17) by cytochrome b5: endocrinological and mechanistic implications. Lee-Robichaud, P., Wright, J.N., Akhtar, M.E., Akhtar, M. Biochem. J. (1995) [Pubmed]
  3. Monoclonal antibodies to rat liver microsomal cytochrome b5. Park, S.S., Walker, W., Aoyama, T., Lapenson, D.P., Waxman, D.J., Gonzalez, F.J., Gelboin, H.V. Biochem. Pharmacol. (1992) [Pubmed]
  4. In-vitro evidence for the regulation of 17,20-lyase activity by cytochrome b5 in adrenocortical adenomas from patients with Cushing's syndrome. Sakai, Y., Yanase, T., Hara, T., Takayanagi, R., Haji, M., Nawata, H. Clin. Endocrinol. (Oxf) (1994) [Pubmed]
  5. Tissue specificity of induction of hamster monooxygenase activity by ethanol. Ueng, T.H., Ju, J.M., Tsai, J.N. Proc. Natl. Sci. Counc. Repub. China B (1989) [Pubmed]
  6. NMR characterization of surface interactions in the cytochrome b5-cytochrome c complex. Burch, A.M., Rigby, S.E., Funk, W.D., MacGillivray, R.T., Mauk, M.R., Mauk, A.G., Moore, G.R. Science (1990) [Pubmed]
  7. Cytochrome P-450 3A4: regulation and role in drug metabolism. Guengerich, F.P. Annu. Rev. Pharmacol. Toxicol. (1999) [Pubmed]
  8. Selective reduction of hepatic cytochrome P450 content in patients with intrahepatic cholestasis. A mechanism for impairment of microsomal drug oxidation. Kawata, S., Imai, Y., Inada, M., Tamura, S., Miyoshi, S., Nishikawa, M., Minami, Y., Tarui, S. Gastroenterology (1987) [Pubmed]
  9. Bcl-2 mutants with restricted subcellular location reveal spatially distinct pathways for apoptosis in different cell types. Zhu, W., Cowie, A., Wasfy, G.W., Penn, L.Z., Leber, B., Andrews, D.W. EMBO J. (1996) [Pubmed]
  10. Binding of cytochrome b5 to membranes of isolated subcellular organelles from rat liver. Remacle, J. J. Cell Biol. (1978) [Pubmed]
  11. Immunohistochemical study of cytochrome b5 in human adrenal gland and in adrenocortical adenomas from patients with Cushing's syndrome. Yanase, T., Sasano, H., Yubisui, T., Sakai, Y., Takayanagi, R., Nawata, H. Endocr. J. (1998) [Pubmed]
  12. Biphasic effects of the flavonoids quercetin and naringenin on the metabolic activation of 2-amino-3,5-dimethylimidazo[4,5-f]quinoline by Salmonella typhimurium TA1538 co-expressing human cytochrome P450 1A2, NADPH-cytochrome P450 reductase, and cytochrome b5. Kang, I.H., Kim, H.J., Oh, H., Park, Y.I., Dong, M.S. Mutat. Res. (2004) [Pubmed]
  13. Mixed function oxidase enzymes in human normal granulocytes and chronic myeloid leukemia cells. I. Detection and estimation. Mungikar, A.M., Zingde, S.M., Advani, S.H., Gothoskar, B.P. Biochemical medicine. (1983) [Pubmed]
  14. Modulation of redox potential in electron transfer proteins: effects of complex formation on the active site microenvironment of cytochrome b5. Wirtz, M., Oganesyan, V., Zhang, X., Studer, J., Rivera, M. Faraday Discuss. (2000) [Pubmed]
  15. Regulation of 17,20 lyase activity by cytochrome b5 and by serine phosphorylation of P450c17. Pandey, A.V., Miller, W.L. J. Biol. Chem. (2005) [Pubmed]
  16. The human cytochrome b5 gene and two of its pseudogenes are located on chromosomes 18q23, 14q31-32.1 and 20p11.2, respectively. Giordano, S.J., Yoo, M., Ward, D.C., Bhatt, M., Overhauser, J., Steggles, A.W. Hum. Genet. (1993) [Pubmed]
  17. Chromosomal localization of a cytochrome b5 gene to human chromosome 18 and a cytochrome b5 pseudogene to the X chromosome. Shephard, E.A., Povey, S., Spurr, N.K., Phillips, I.R. Genomics (1991) [Pubmed]
  18. The human liver and reticulocyte cytochrome b5 mRNAs are products from a single gene. Giordano, S.J., Steggles, A.W. Biochem. Biophys. Res. Commun. (1991) [Pubmed]
  19. Cytochrome b5 augments the 17,20-lyase activity of human P450c17 without direct electron transfer. Auchus, R.J., Lee, T.C., Miller, W.L. J. Biol. Chem. (1998) [Pubmed]
  20. Regulation of cytochrome b5 gene transcription by Sp3, GATA-6, and steroidogenic factor 1 in human adrenal NCI-H295A cells. Huang, N., Dardis, A., Miller, W.L. Mol. Endocrinol. (2005) [Pubmed]
  21. Control of androgen biosynthesis in the human through the interaction of Arg347 and Arg358 of CYP17 with cytochrome b5. Lee-Robichaud, P., Akhtar, M.E., Akhtar, M. Biochem. J. (1998) [Pubmed]
  22. Diaphorase P: a new fetal isozyme identified in human placenta. Choury, D., Kaplan, J.C. Biochim. Biophys. Acta (1980) [Pubmed]
  23. Purification and characterization of the human neutrophil NADH-cytochrome b5 reductase. Tauber, A.I., Wright, J., Higson, F.K., Edelman, S.A., Waxman, D.J. Blood (1985) [Pubmed]
  24. Modulation of CYP1A1-mediated oxidation of carcinogenic azo dye Sudan I and its binding to DNA by cytochrome b5. Stiborova, M., Martinek, V., Schmeiser, H.H., Frei, E. Neuro Endocrinol. Lett. (2006) [Pubmed]
  25. Lysine mutagenesis identifies cationic charges of human CYP17 that interact with cytochrome b5 to promote male sex-hormone biosynthesis. Lee-Robichaud, P., Akhtar, M.E., Akhtar, M. Biochem. J. (1999) [Pubmed]
  26. Electrostatic properties deduced from refined structures of NADH-cytochrome b5 reductase and the other flavin-dependent reductases: pyridine nucleotide-binding and interaction with an electron-transfer partner. Nishida, H., Miki, K. Proteins (1996) [Pubmed]
  27. Activation of phenacetin O-deethylase activity by alpha-naphthoflavone in human liver microsomes. Nakajima, M., Kobayashi, K., Oshima, K., Shimada, N., Tokudome, S., Chiba, K., Yokoi, T. Xenobiotica (1999) [Pubmed]
  28. The primate adrenal zona reticularis is defined by expression of cytochrome b5, 17alpha-hydroxylase/17,20-lyase cytochrome P450 (P450c17) and NADPH-cytochrome P450 reductase (reductase) but not 3beta-hydroxysteroid dehydrogenase/delta5-4 isomerase (3beta-HSD). Mapes, S., Corbin, C.J., Tarantal, A., Conley, A. J. Clin. Endocrinol. Metab. (1999) [Pubmed]
  29. 16Alpha-hydroxylation of estrone by human cytochrome P4503A4/5. Huang, Z., Guengerich, F.P., Kaminsky, L.S. Carcinogenesis (1998) [Pubmed]
  30. Optimization of yeast-expressed human liver cytochrome P450 3A4 catalytic activities by coexpressing NADPH-cytochrome P450 reductase and cytochrome b5. Peyronneau, M.A., Renaud, J.P., Truan, G., Urban, P., Pompon, D., Mansuy, D. Eur. J. Biochem. (1992) [Pubmed]
  31. Baculovirus expression and purification of human and rat cytochrome P450 2E1. Chen, W., Peter, R.M., McArdle, S., Thummel, K.E., Sigle, R.O., Nelson, S.D. Arch. Biochem. Biophys. (1996) [Pubmed]
  32. Redundancy in the pathway for redox regulation of mammalian methionine synthase: reductive activation by the dual flavoprotein, novel reductase 1. Olteanu, H., Banerjee, R. J. Biol. Chem. (2003) [Pubmed]
  33. NCB5OR is a novel soluble NAD(P)H reductase localized in the endoplasmic reticulum. Zhu, H., Larade, K., Jackson, T.A., Xie, J., Ladoux, A., Acker, H., Berchner-Pfannschmidt, U., Fandrey, J., Cross, A.R., Lukat-Rodgers, G.S., Rodgers, K.R., Bunn, H.F. J. Biol. Chem. (2004) [Pubmed]
  34. Assessment of porcine and human 16-ene-synthase, a third activity of P450c17, in the formation of an androstenol precursor. Role of recombinant cytochrome b5 and P450 reductase. Soucy, P., Lacoste, L., Luu-The, V. Eur. J. Biochem. (2003) [Pubmed]
  35. Formation of guanoxabenz from guanabenz in human liver. A new metabolic marker for CYP1A2. Clement, B., Demesmaeker, M. Drug Metab. Dispos. (1997) [Pubmed]
  36. Purification and characterization of human liver cytochrome P-450-ALC. Lasker, J.M., Raucy, J., Kubota, S., Bloswick, B.P., Black, M., Lieber, C.S. Biochem. Biophys. Res. Commun. (1987) [Pubmed]
  37. Affinity chromatography of microsomal enzymes on immobilized detergent-solubilized cytochrome b5. Kawata, S., Trzaskos, J.M., Gaylor, J.L. J. Biol. Chem. (1986) [Pubmed]
  38. Magnetic circular dichroism studies of low-spin cytochromes. Temperature dependence and effects of axial coordination on the spectra of cytochrome c and cytochrome b5. Vickery, L., Nozawa, T., Sauer, K. J. Am. Chem. Soc. (1976) [Pubmed]
WikiGenes - Universities