View source for NAD+ kinase

{{short description|Enzyme}}
{{DISPLAYTITLE:NAD<sup>+</sup> kinase}}
{{infobox enzyme
| Name       = NAD<sup>+</sup> kinase
| EC_number  = 2.7.1.23
| CAS_number = 9032-66-0
| GO_code    = 0003951
| image      = NADK.png
| width      =
| caption    = [[Ribbon diagram]] of NAD<sup>+</sup> kinase in complex with substrates.<ref name="pmid16242716">{{PDB|1SUW}}; {{cite journal | vauthors = Liu J, Lou Y, Yokota H, Adams PD, Kim R, Kim SH | title = Crystal structures of an NAD kinase from Archaeoglobus fulgidus in complex with ATP, NAD, or NADP | journal = Journal of Molecular Biology | volume = 354 | issue = 2 | pages = 289–303 | date = Nov 2005 | pmid = 16242716 | doi = 10.1016/j.jmb.2005.09.026 | url = https://zenodo.org/record/1259129 }}</ref> 
}}
{{Infobox_gene}}

'''NAD<sup>+</sup> kinase''' (EC 2.7.1.23, NADK) is an enzyme that converts [[nicotinamide adenine dinucleotide]] (NAD<sup>+</sup>) into [[Nicotinamide adenine dinucleotide phosphate|NADP<sup>+</sup>]] through phosphorylating the NAD<sup>+</sup> [[coenzyme]].<ref>{{cite journal | vauthors = Magni G, Orsomando G, Raffaelli N | title = Structural and functional properties of NAD kinase, a key enzyme in NADP biosynthesis | journal = Mini Reviews in Medicinal Chemistry | volume = 6 | issue = 7 | pages = 739–46 | date = Jul 2006 | pmid = 16842123 | doi = 10.2174/138955706777698688 }}</ref> NADP<sup>+</sup> is an essential coenzyme that is reduced to NADPH primarily by the [[pentose phosphate pathway]] to provide reducing power in biosynthetic processes such as [[fatty acid biosynthesis]] and [[nucleotide synthesis]].<ref>{{cite journal | vauthors = Pollak N, Dölle C, Ziegler M | title = The power to reduce: pyridine nucleotides--small molecules with a multitude of functions | journal = The Biochemical Journal | volume = 402 | issue = 2 | pages = 205–18 | date = Mar 2007 | pmid = 17295611 | pmc = 1798440 | doi = 10.1042/BJ20061638 }}</ref> The structure of the NADK from the [[archaea]]n ''[[Archaeoglobus|Archaeoglobus fulgidus]]'' has been determined.<ref name="pmid16242716"/>

In humans, the [[genes]] ''NADK''<ref name="pmid11594753">{{cite journal | vauthors = Lerner F, Niere M, Ludwig A, Ziegler M | title = Structural and functional characterization of human NAD kinase | journal = Biochemical and Biophysical Research Communications | volume = 288 | issue = 1 | pages = 69–74 | date = Oct 2001 | pmid = 11594753 | doi = 10.1006/bbrc.2001.5735 }}</ref> and ''MNADK''<ref name="pmid25641397">{{cite journal | vauthors = Zhang R | title = MNADK, a Long-Awaited Human Mitochondrion-Localized NAD Kinase | journal = Journal of Cellular Physiology | volume = 230 | issue = 8 | pages = 1697–701 | date = Aug 2015 | pmid = 25641397 | doi = 10.1002/jcp.24926 | s2cid = 11539186 }}</ref> encode NAD<sup>+</sup> kinases localized in cytosol<ref name="pmid11594753"/> and mitochondria,<ref name="pmid25641397"/> respectively. Similarly, yeast have both cytosolic and mitochondrial isoforms, and the yeast mitochondrial isoform accepts both NAD<sup>+</sup> and NADH as substrates for phosphorylation.<ref>{{cite journal | vauthors = Iwahashi Y, Hitoshio A, Tajima N, Nakamura T | title = Characterization of NADH kinase from Saccharomyces cerevisiae | journal = Journal of Biochemistry | volume = 105 | issue = 4 | pages = 588–93 | date = Apr 1989 | pmid = 2547755 | doi = 10.1093/oxfordjournals.jbchem.a122709 }}</ref><ref>{{cite journal | vauthors = Iwahashi Y, Nakamura T | title = Localization of the NADH kinase in the inner membrane of yeast mitochondria | journal = Journal of Biochemistry | volume = 105 | issue = 6 | pages = 916–21 | date = Jun 1989 | pmid = 2549021 | doi = 10.1093/oxfordjournals.jbchem.a122779 }}</ref>

== Reaction ==
The reaction catalyzed by NADK is

: [[Adenosine triphosphate|ATP]] + [[Nicotinamide adenine dinucleotide|NAD<sup>+</sup>]] <math>\rightleftharpoons</math> [[Adenosine diphosphate|ADP]] + [[Nicotinamide adenine dinucleotide phosphate|NADP<sup>+</sup>]]

== Mechanism ==

NADK phosphorylates NAD<sup>+</sup> at the 2’ position of the ribose ring that carries the adenine moiety. It is highly selective for its substrates, NAD and ATP, and does not tolerate modifications either to the phosphoryl acceptor, NAD, or the pyridine moiety of the phosphoryl donor, ATP.<ref name="pmid11594753" /> NADK also uses metal ions to coordinate the ATP in the active site. In vitro studies with various divalent metal ions have shown that zinc and manganese are preferred over magnesium, while copper and nickel are not accepted by the enzyme at all.<ref name="pmid11594753" /> A proposed mechanism involves the 2' alcohol oxygen acting as a nucleophile to attack the gamma-phosphoryl of ATP, releasing ADP.

[[File:NADK mechanism.png|none|thumb|Proposed mechanism of action for NAD<sup>+</sup> phosphorylation by NADK]]

== Regulation ==

NADK is highly regulated by the redox state of the cell. Whereas NAD is predominantly found in its oxidized state NAD<sup>+</sup>, the phosphorylated NADP is largely present in its reduced form, as NADPH.<ref>{{cite journal | vauthors = Burch HB, Bradley ME, Lowry OH | title = The measurement of triphosphopyridine nucleotide and reduced triphosphopyridine nucleotide and the role of hemoglobin in producing erroneous triphosphopyridine nucleotide values | journal = The Journal of Biological Chemistry | volume = 242 | issue = 19 | pages = 4546–54 | date = Oct 1967 | doi = 10.1016/S0021-9258(18)99573-6 | pmid = 4383634 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Veech RL, Eggleston LV, Krebs HA | title = The redox state of free nicotinamide-adenine dinucleotide phosphate in the cytoplasm of rat liver | journal = The Biochemical Journal | volume = 115 | issue = 4 | pages = 609–19 | date = Dec 1969 | pmid = 4391039 | pmc = 1185185 | doi=10.1042/bj1150609a}}</ref> Thus, NADK can modulate responses to oxidative stress by controlling NADP synthesis. Bacterial NADK is shown to be inhibited allosterically by both NADPH and NADH.<ref>{{cite journal | vauthors = Grose JH, Joss L, Velick SF, Roth JR | title = Evidence that feedback inhibition of NAD kinase controls responses to oxidative stress | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 103 | issue = 20 | pages = 7601–6 | date = May 2006 | pmid = 16682646 | pmc = 1472491 | doi = 10.1073/pnas.0602494103 | bibcode = 2006PNAS..103.7601G | doi-access = free }}</ref> NADK is also reportedly stimulated by [[calcium]]/[[Calmodulin 1|calmodulin]] binding in certain cell types, such as neutrophils.<ref>{{cite journal | vauthors = Williams MB, Jones HP | title = Calmodulin-dependent NAD kinase of human neutrophils | journal = Archives of Biochemistry and Biophysics | volume = 237 | issue = 1 | pages = 80–7 | date = Feb 1985 | pmid = 2982330 | doi=10.1016/0003-9861(85)90256-5}}</ref> NAD kinases in plants and sea urchin eggs have also been found to bind calmodulin.<ref>{{cite journal | vauthors = Lee SH, Seo HY, Kim JC, Heo WD, Chung WS, Lee KJ, Kim MC, Cheong YH, Choi JY, Lim CO, Cho MJ | title = Differential activation of NAD kinase by plant calmodulin isoforms. The critical role of domain I | journal = The Journal of Biological Chemistry | volume = 272 | issue = 14 | pages = 9252–9 | date = Apr 1997 | pmid = 9083059 | doi = 10.1074/jbc.272.14.9252 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Epel D, Patton C, Wallace RW, Cheung WY | title = Calmodulin activates NAD kinase of sea urchin eggs: an early event of fertilization | journal = Cell | volume = 23 | issue = 2 | pages = 543–9 | date = Feb 1981 | pmid = 6258805 | doi=10.1016/0092-8674(81)90150-1| s2cid = 44821877 }}</ref>

== Clinical significance ==

Due to the essential role of NADPH in lipid and DNA biosynthesis and the hyperproliferative nature of most cancers, NADK is an attractive target for cancer therapy. Furthermore, NADPH is required for the antioxidant activities of [[thioredoxin reductase]] and [[glutaredoxin]].<ref>{{cite journal | vauthors = Lu J, Holmgren A | title = The thioredoxin antioxidant system | journal = Free Radical Biology & Medicine | volume = 66 | pages = 75–87 | date = Jan 2014 | pmid = 23899494 | doi = 10.1016/j.freeradbiomed.2013.07.036 }}</ref><ref>{{cite journal | vauthors = Estrela JM, Ortega A, Obrador E | title = Glutathione in cancer biology and therapy | journal = Critical Reviews in Clinical Laboratory Sciences | volume = 43 | issue = 2 | pages = 143–81 | date = 2006-01-01 | pmid = 16517421 | doi = 10.1080/10408360500523878 | s2cid = 8962293 }}</ref> Thionicotinamide and other [[nicotinamide]] analogs are potential inhibitors of NADK,<ref>{{cite journal | vauthors = Hsieh YC, Tedeschi P, Adebisi Lawal R, Banerjee D, Scotto K, Kerrigan JE, Lee KC, Johnson-Farley N, Bertino JR, Abali EE | title = Enhanced degradation of dihydrofolate reductase through inhibition of NAD kinase by nicotinamide analogs | journal = Molecular Pharmacology | volume = 83 | issue = 2 | pages = 339–53 | date = Feb 2013 | pmid = 23197646 | pmc = 3558814 | doi = 10.1124/mol.112.080218 }}</ref> and studies show that treatment of colon cancer cells with thionicotinamide suppresses the cytosolic NADPH pool to increase oxidative stress and synergizes with chemotherapy.<ref>{{cite journal | vauthors = Tedeschi PM, Lin H, Gounder M, Kerrigan JE, Abali EE, Scotto K, Bertino JR | title = Suppression of Cytosolic NADPH Pool by Thionicotinamide Increases Oxidative Stress and Synergizes with Chemotherapy | journal = Molecular Pharmacology | volume = 88 | issue = 4 | pages = 720–7 | date = Oct 2015 | pmid = 26219913 | pmc = 4576680 | doi = 10.1124/mol.114.096727 }}</ref>

While the role of NADK in increasing the NADPH pool appears to offer protection against [[apoptosis]], there are also cases where NADK activity appears to potentiate cell death. Genetic studies done in human haploid cell lines indicate that knocking out NADK may protect from certain non-apoptotic stimuli.<ref>{{cite journal | vauthors = Dixon SJ, Winter GE, Musavi LS, Lee ED, Snijder B, Rebsamen M, Superti-Furga G, Stockwell BR | title = Human Haploid Cell Genetics Reveals Roles for Lipid Metabolism Genes in Nonapoptotic Cell Death | journal = ACS Chemical Biology | volume = 10 | issue = 7 | pages = 1604–9 | date = Jul 2015 | pmid = 25965523 | pmc = 4509420 | doi = 10.1021/acschembio.5b00245 }}</ref>

== See also ==
{{Portal|Biology}}
*[[Oxidative phosphorylation]]
*[[Electron transport chain]]
*[[Metabolism]]

== References ==
{{reflist}}

== Further reading ==
{{refbegin|33em}}
* {{cite journal | vauthors = Andersson B, Wentland MA, Ricafrente JY, Liu W, Gibbs RA | title = A "double adaptor" method for improved shotgun library construction | journal = Analytical Biochemistry | volume = 236 | issue = 1 | pages = 107–13 | date = Apr 1996 | pmid = 8619474 | doi = 10.1006/abio.1996.0138 }}
* {{cite journal | vauthors = Yu W, Andersson B, Worley KC, Muzny DM, Ding Y, Liu W, Ricafrente JY, Wentland MA, Lennon G, Gibbs RA | title = Large-scale concatenation cDNA sequencing | journal = Genome Research | volume = 7 | issue = 4 | pages = 353–8 | date = Apr 1997 | pmid = 9110174 | pmc = 139146 | doi = 10.1101/gr.7.4.353 }}
* {{cite journal | vauthors = Stelzl U, Worm U, Lalowski M, Haenig C, Brembeck FH, Goehler H, Stroedicke M, Zenkner M, Schoenherr A, Koeppen S, Timm J, Mintzlaff S, Abraham C, Bock N, Kietzmann S, Goedde A, Toksöz E, Droege A, Krobitsch S, Korn B, Birchmeier W, Lehrach H, Wanker EE | title = A human protein-protein interaction network: a resource for annotating the proteome | journal = Cell | volume = 122 | issue = 6 | pages = 957–68 | date = Sep 2005 | pmid = 16169070 | doi = 10.1016/j.cell.2005.08.029 | hdl = 11858/00-001M-0000-0010-8592-0 | s2cid = 8235923 | hdl-access = free }}
* {{cite journal | vauthors = Pollak N, Niere M, Ziegler M | title = NAD kinase levels control the NADPH concentration in human cells | journal = The Journal of Biological Chemistry | volume = 282 | issue = 46 | pages = 33562–71 | date = Nov 2007 | pmid = 17855339 | doi = 10.1074/jbc.M704442200 | doi-access = free | hdl = 1956/3161 | hdl-access = free }}
{{refend}}

== External links ==
*[http://au.expasy.org/enzyme/2.7.1.23 ENZYME entry on EC 2.7.1.23]
*[http://www.brenda-enzymes.org/php/result_flat.php4?ecno=2.7.1.23 BRENDA entry on EC 2.7.1.23]
* [https://www.ebi.ac.uk/pdbe/pdbe-kb/proteins/O95544 PDBe-KB] provides an overview of all the structure information available in the PDB for Human NAD kinase

{{Kinases}}
{{Enzymes}}

{{DEFAULTSORT:Nad+ Kinase}}
[[Category:EC 2.7.1]]
[[Category:Cellular respiration]]
[[Category:Metabolism]]