Adrenodoxin reductase explained

Adrenodoxin reductase (Enzyme Nomenclature name: adrenodoxin-NADP+ reductase, EC 1.18.1.6), was first isolated from bovine adrenal cortex where it functions as the first enzyme in the mitochondrial P450 systems that catalyze essential steps in steroid hormone biosynthesis.^{[1] [2]} Examination of complete genome sequences revealed that adrenodoxin reductase gene is present in most metazoans and prokaryotes.^[3]

Nomenclature

The name of the enzyme was coined based on its function to reduce a [2Fe-2S] (2 iron, 2 sulfur) electron-transfer protein that was named adrenodoxin. Later, in some studies, the enzyme was also referred to as a "ferredoxin reductase", as adrenodoxin is a ferredoxin. In the human gene nomenclature, the standard name is ferredoxin reductase and the symbol is FDXR, with ADXR specified as a synonym.

The assignment of the name "ferredoxin reductase" has been criticized as a misnomer because determination of the structure of adrenodoxin reductase revealed that it is completely different from that of plant ferredoxin reductase and there is no homology between these two enzymes.^{[4] [5] [6]} With more proteins with a ferroxodin-reducing activity discovered in both families as well as novel families, this enzyme activity is now seen as an example of convergent evolution.^{[7] [8]}

Function

Adrenodoxin reductase is a flavoprotein as it carries a FAD type coenzyme. The enzyme functions as the first electron transfer protein of mitochondrial P450 systems such as P450scc. The FAD coenzyme receives two electrons from NADPH and transfers them one at a time to the electron transfer protein adrenodoxin.^[9] Adrenodoxin functions as a mobile shuttle that transfers electrons between ADXR and mitochondrial P450s.^[10]

It catalyzes the following reaction:

NADPH + 2 oxidized adrenodoxin —→ 2 reduced adrenodoxin + NADP + H

Gene structure

The cDNA for adrenodoxin reductase was first cloned in 1987.^[11] In both bovine and human genomes there is only a single copy of the gene.^[12]

Sites of expression

ADXR gene is expressed in all tissues that have mitochondrial P450s. The highest levels of the enzyme are found in the adrenal cortex, granulosa cells of the ovary and leydig cells of the testis that specialize in steroid hormone synthesis.^{[2] [13]} Immmunofluorescent staining shows that enzyme is localized in mitochondria.^[14] The enzyme is also expressed in the liver, the kidney and the placenta.

Enzyme structure

Adrenodoxin reductase has two domains that bind NADPH and FAD separately. The FAD and NADP binding sites of the enzyme were predicted by sequence analysis of the enzyme.^[15]

While the FAD-binding site has a consensus sequence (Gly-x-Gly-x-x-Gly) that is similar to other Rossmann folds in FAD and NAD binding sites,^[16] the NADPH binding site consensus sequence differs from the FAD-binding site by the substitution of an alanine instead of the last Gly (Gly-x-Gly-x-x-Ala). The location of these FAD and NADP binding sites were confirmed by the crystal structure of the enzyme.

Further reading

• Sparkes RS, Klisak I, Miller WL . Regional mapping of genes encoding human steroidogenic enzymes: P450scc to 15q23-q24, adrenodoxin to 11q22; adrenodoxin reductase to 17q24-q25; and P450c17 to 10q24-q25 . DNA and Cell Biology . 10 . 5 . 359–65 . Jun 1991 . 1863359 . 10.1089/dna.1991.10.359 .
• Coghlan VM, Vickery LE . Site-specific mutations in human ferredoxin that affect binding to ferredoxin reductase and cytochrome P450scc . The Journal of Biological Chemistry . 266 . 28 . 18606–12 . Oct 1991 . 10.1016/S0021-9258(18)55106-1 . 1917982 . free .
• Lin D, Shi YF, Miller WL . Cloning and sequence of the human adrenodoxin reductase gene . Proceedings of the National Academy of Sciences of the United States of America . 87 . 21 . 8516–20 . Nov 1990 . 2236061 . 54987 . 10.1073/pnas.87.21.8516 . 1990PNAS...87.8516L . free .
• Usanov SA, Chernogolov AA, Honkakoski P, Lang M, Passanen M, Raunio H, Pelkonen O . [Cholesterol-hydroxylating cytochrome P-450 from bovine adrenal cortex mitochondria and human placenta: immunochemical properties and structural characteristics] . Biokhimiya . 55 . 5 . 865–77 . May 1990 . 2393675 .
• Sasano H, Sasano N, Okamoto M, Nonaka Y . Immunohistochemical demonstration of adrenodoxin reductase in bovine and human adrenals . Pathology, Research and Practice . 184 . 5 . 473–9 . May 1989 . 2748461 . 10.1016/s0344-0338(89)80137-2 .
• Usanov SA, Honkakoski P, Lang MA, Pasanen M, Pelkonen O, Raunio H . Comparison of the immunochemical properties of human placental and bovine adrenal cholesterol side-chain cleavage enzyme complex . Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology . 998 . 2 . 189–95 . Oct 1989 . 2790061 . 10.1016/0167-4838(89)90272-0 .
• Maruyama K, Sugano S . Oligo-capping: a simple method to replace the cap structure of eukaryotic mRNAs with oligoribonucleotides . Gene . 138 . 1–2 . 171–4 . Jan 1994 . 8125298 . 10.1016/0378-1119(94)90802-8 .
• Suzuki Y, Yoshitomo-Nakagawa K, Maruyama K, Suyama A, Sugano S . Construction and characterization of a full length-enriched and a 5'-end-enriched cDNA library . Gene . 200 . 1–2 . 149–56 . Oct 1997 . 9373149 . 10.1016/S0378-1119(97)00411-3 .
• Müller JJ, Lapko A, Bourenkov G, Ruckpaul K, Heinemann U . Adrenodoxin reductase-adrenodoxin complex structure suggests electron transfer path in steroid biosynthesis . The Journal of Biological Chemistry . 276 . 4 . 2786–9 . Jan 2001 . 11053423 . 10.1074/jbc.M008501200 . free .
• Gonzalez MI, Robins DM . Oct-1 preferentially interacts with androgen receptor in a DNA-dependent manner that facilitates recruitment of SRC-1 . The Journal of Biological Chemistry . 276 . 9 . 6420–8 . Mar 2001 . 11096094 . 10.1074/jbc.M008689200 . free .
• Tuckey RC, Headlam MJ . Placental cytochrome P450scc (CYP11A1): comparison of catalytic properties between conditions of limiting and saturating adrenodoxin reductase . The Journal of Steroid Biochemistry and Molecular Biology . 81 . 2 . 153–8 . Jun 2002 . 12137805 . 10.1016/S0960-0760(02)00058-4 . 44273641 .
• Liu G, Chen X . The ferredoxin reductase gene is regulated by the p53 family and sensitizes cells to oxidative stress-induced apoptosis . Oncogene . 21 . 47 . 7195–204 . Oct 2002 . 12370809 . 10.1038/sj.onc.1205862 . free .
• Araya Z, Hosseinpour F, Bodin K, Wikvall K . Metabolism of 25-hydroxyvitamin D3 by microsomal and mitochondrial vitamin D3 25-hydroxylases (CYP2D25 and CYP27A1): a novel reaction by CYP27A1 . Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids . 1632 . 1–3 . 40–7 . Jun 2003 . 12782149 . 10.1016/S1388-1981(03)00062-3 .
• Thiboutot D, Jabara S, McAllister JM, Sivarajah A, Gilliland K, Cong Z, Clawson G . Human skin is a steroidogenic tissue: steroidogenic enzymes and cofactors are expressed in epidermis, normal sebocytes, and an immortalized sebocyte cell line (SEB-1) . The Journal of Investigative Dermatology . 120 . 6 . 905–14 . Jun 2003 . 12787114 . 10.1046/j.1523-1747.2003.12244.x . free .
• Kimura K, Wakamatsu A, Suzuki Y, Ota T, Nishikawa T, Yamashita R, Yamamoto J, Sekine M, Tsuritani K, Wakaguri H, Ishii S, Sugiyama T, Saito K, Isono Y, Irie R, Kushida N, Yoneyama T, Otsuka R, Kanda K, Yokoi T, Kondo H, Wagatsuma M, Murakawa K, Ishida S, Ishibashi T, Takahashi-Fujii A, Tanase T, Nagai K, Kikuchi H, Nakai K, Isogai T, Sugano S . Diversification of transcriptional modulation: large-scale identification and characterization of putative alternative promoters of human genes . Genome Research . 16 . 1 . 55–65 . Jan 2006 . 16344560 . 1356129 . 10.1101/gr.4039406 .

Notes and References

1. Omura T, Sanders E, Estabrook RW, Cooper DY, Rosenthal O . Isolation from adrenal cortex of a nonheme iron protein and a flavoprotein functional as a reduced triphosphopyridine nucleotide-cytochrome P-450 reductase. Archives of Biochemistry and Biophysics. December 1966. 117. 3. 660–673. 10.1016/0003-9861(66)90108-1.
2. Hanukoglu I . Steroidogenic enzymes: structure, function, and role in regulation of steroid hormone biosynthesis . The Journal of Steroid Biochemistry and Molecular Biology . 43 . 8 . 779–804 . Dec 1992 . 22217824 . 10.1016/0960-0760(92)90307-5 . 112729 .
3. Hanukoglu I . Conservation of the Enzyme-Coenzyme Interfaces in FAD and NADP Binding Adrenodoxin Reductase-A Ubiquitous Enzyme . Journal of Molecular Evolution . 85 . 5 . 205–218 . 2017 . 29177972 . 10.1007/s00239-017-9821-9 . 2017JMolE..85..205H . 7120148 .
4. Book: Hanukoglu I . Physiological Functions of Cytochrome P450 in Relation to Structure and Regulation . Electron transfer proteins of cytochrome P450 systems . Adv. Mol. Cell Biol. . 1996 . 14 . 29–55 . 10.1016/S1569-2558(08)60339-2 . Advances in Molecular and Cell Biology . 9780762301133 .
5. Ziegler GA, Vonrhein C, Hanukoglu I, Schulz GE . The structure of adrenodoxin reductase of mitochondrial P450 systems: electron transfer for steroid biosynthesis . Journal of Molecular Biology . 289 . 4 . 981–90 . Jun 1999 . 10369776 . 10.1006/jmbi.1999.2807 .
6. Ziegler GA, Schulz GE. Crystal structures of adrenodoxin reductase in complex with NADP+ and NADPH suggesting a mechanism for the electron transfer of an enzyme family. . Biochemistry . 2000 . 39 . 36 . 10986–95 . 10998235 . 10.1021/bi000079k.
7. Aliverti A, Pandini V, Pennati A, de Rosa M, Zanetti G . Structural and functional diversity of ferredoxin-NADP(+) reductases . Archives of Biochemistry and Biophysics . 474 . 2 . 283–91 . June 2008 . 18307973 . 10.1016/j.abb.2008.02.014 . free . 2434/41439 .
8. Spaans SK, Weusthuis RA, van der Oost J, Kengen SW . NADPH-generating systems in bacteria and archaea . Frontiers in Microbiology . 6 . 742 . 2015 . 26284036 . 4518329 . 10.3389/fmicb.2015.00742 . free .
9. Lambeth JD, Kamin H . Adrenodoxin reductase. Properties of the complexes of reduced enzyme with NADP+ and NADPH . The Journal of Biological Chemistry . 251 . 14 . 4299–306 . Jul 1976 . 10.1016/S0021-9258(17)33296-9 . 6475 . free .
10. Hanukoglu I, Jefcoate CR . Mitochondrial cytochrome P-450scc. Mechanism of electron transport by adrenodoxin . The Journal of Biological Chemistry . 255 . 7 . 3057–61 . Apr 1980 . 10.1016/S0021-9258(19)85851-9 . 6766943 . free .
11. Hanukoglu I, Gutfinger T, Haniu M, Shively JE . Isolation of a cDNA for adrenodoxin reductase (ferredoxin-NADP+ reductase). Implications for mitochondrial cytochrome P-450 systems. . European Journal of Biochemistry . 169 . 3 . 449–455 . Dec 1987 . 10.1111/j.1432-1033.1987.tb13632.x . 3691502 . free .
12. Solish SB, Picado-Leonard J, Morel Y, Kuhn RW, Mohandas TK, Hanukoglu I, Miller WL . Human adrenodoxin reductase: two mRNAs encoded by a single gene on chromosome 17cen----q25 are expressed in steroidogenic tissues . Proceedings of the National Academy of Sciences of the United States of America . 85 . 19 . 7104–7108 . Oct 1988 . 2845396 . 282132 . 10.1073/pnas.85.19.7104 . 1988PNAS...85.7104S . free .
13. Hanukoglu I, Hanukoglu Z . Stoichiometry of mitochondrial cytochromes P-450, adrenodoxin and adrenodoxin reductase in adrenal cortex and corpus luteum. Implications for membrane organization and gene regulation . European Journal of Biochemistry . 157 . 1 . 27–31 . May 1986 . 3011431 . 10.1111/j.1432-1033.1986.tb09633.x . free .
14. Hanukoglu I, Suh BS, Himmelhoch S, Amsterdam A . Induction and mitochondrial localization of cytochrome P450scc system enzymes in normal and transformed ovarian granulosa cells . The Journal of Cell Biology . 111 . 4 . 1373–81 . October 1990 . 2170421 . 2116250 . 10.1083/jcb.111.4.1373 .
15. Hanukoglu I, Gutfinger T . cDNA sequence of adrenodoxin reductase. Identification of NADP-binding sites in oxidoreductases . European Journal of Biochemistry . 180 . 2 . 479–84 . Mar 1989 . 2924777 . 10.1111/j.1432-1033.1989.tb14671.x . free .
16. Hanukoglu I . Proteopedia: Rossmann fold: A beta-alpha-beta fold at dinucleotide binding sites . Biochem Mol Biol Educ . 43 . 3 . 206–209 . 2015 . 25704928 . 10.1002/bmb.20849 . 11857160 . free .