MetaCyc Enzyme: cytosolic 5'-nucleotidase II

Gene: NT5C2 Accession Number: G-11606 (MetaCyc)

Synonyms: NT5B, NT5CP, PNT5, 5'-nucleotidase cytosolic II, cN-II, high Km 5'-NT, purine 5'-NT, GMP,IMP-specific 5'-NT

Species: Homo sapiens

Subunit composition of cytosolic 5'-nucleotidase II = [NT5C2]4
         cytosolic 5'-nucleotidase II subunit = NT5C2

The native apparent molecular mass was determined by gel filtration chromatography [Spychala88].

The 5'-nucleotidases are a family of enzymes from both prokaryotic and eukaryotic sources. They catalyze dephsophorylation of nucleoside monophosphates and have a role in the regulation of nucleotide and nucleoside levels. They are also of clinical interest due to their ability to inhibit the activation of nucleoside analog drugs that are used in anticancer and antiviral drug therapy. These analogs are activated by kinase-catalyzed phosphorylation. Reviewed in [Hunsucker05].

Human 5'-nucleotidases identified to date include ecto-5'-nucleotidase; cytosolic 5'-nucleotidases 1A, 1B, II, and III; cytosolic 5'(3')-deoxyribonucleotidase; and mitochondrial 5'(3')-deoxyribonucleotidase. The ecto-5'-nucleotidase is attached to the outer plasma membrane. The human 5'-nucleotidases also vary in substrate specificity and tissue expression. ecto-5'-nucleotidase, cytosolic 5'-nucleotidase II, cytosolic 5'(3')-deoxyribonucleotidase and mitochondrial 5'(3')-deoxyribonucleotidase are expressed in many tissues, whereas cytosolic 5'-nucleotidases 1A, 1B and III are more tissue-specific in their expression. Evidence suggests that human cytosolic 5'-nucleotidase 1A functions in AMP catabolism, while cytosolic 5'-nucleotidase II functions in IMP and GMP catabolism due to its preference for the 6-hydroxypurine nucleoside monophosphate substrates IMP, dIMP, GMP, dGMP and XMP. Reviewed in [Hunsucker05, Borowiec06, Bianchi03].

Human cytosolic 5'-nucleotidase II also has phosphotransferase activity and can catalyze the reverse reaction under certain conditions (in [Wallden07, Hunsucker05]). The enzyme is homotetrameric (reviewed in [Hunsucker05, Bianchi03]). The crystal structure of this enzyme has been determined [Wallden07].
The subunit apparent molecular mass was determined by SDS-PAGE [Spychala88].

Gene Citations: [Oka94]

Locations: cytosol

Map Position: [104,845,940 <- 104,953,056]

Molecular Weight of Polypeptide: 64.97 kD (from nucleotide sequence), 53.0 kD (experimental) [Spychala88 ]

Molecular Weight of Multimer: 210.0 kD (experimental) [Spychala88]

Unification Links: ArrayExpress:P49902 , Entrez-gene:22978 , Mint:MINT-1436872 , PhosphoSite:P49902 , PhylomeDB:P49902 , Pride:P49902 , Protein Model Portal:P49902 , SMR:P49902 , String:9606.ENSP00000339479 , UniProt:P49902

Relationship Links: InterPro:IN-FAMILY:IPR008380 , InterPro:IN-FAMILY:IPR016695 , InterPro:IN-FAMILY:IPR023214 , Panther:IN-FAMILY:PTHR12103 , PDB:Structure:2CN1 , PDB:Structure:2J2C , PDB:Structure:2JC9 , PDB:Structure:2JCM , PDB:Structure:2VKQ , PDB:Structure:2XCV , PDB:Structure:2XCW , PDB:Structure:2XCX , PDB:Structure:2XJB , PDB:Structure:2XJC , PDB:Structure:2XJD , PDB:Structure:2XJE , PDB:Structure:2XJF , PDB:Structure:4H4B , Pfam:IN-FAMILY:PF05761

Gene-Reaction Schematic: ?

Gene-Reaction Schematic

Instance reactions of [a ribonucleoside 5'-monophosphate + H2O → a ribonucleoside + phosphate] (
i1: GMP + H2O → guanosine + phosphate (

i2: IMP + H2O → inosine + phosphate (

i3: CMP + H2O → cytidine + phosphate (

i4: UMP + H2O → uridine + phosphate (

i5: XMP + H2O → xanthosine + phosphate (

i6: AMP + H2O → adenosine + phosphate (

GO Terms:

Cellular Component: GO:0005829 - cytosol [Spychala88]

Created 16-Oct-2009 by Fulcher CA , SRI International

Enzymatic reaction of: XMP 5'-nucleotidase (cytosolic 5'-nucleotidase II)

XMP + H2O <=> xanthosine + phosphate

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is physiologically favored in the direction shown.

In Pathways: purine nucleotides degradation II (aerobic) , urate biosynthesis/inosine 5'-phosphate degradation

This enzyme was shown to use XMP as a substrate, although at only 23% of the activity with IMP as substrate [Spychala88].

Enzymatic reaction of: GMP 5'-nucleotidase (cytosolic 5'-nucleotidase II)

GMP + H2O <=> guanosine + phosphate

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is physiologically favored in the direction shown.

Alternative Substrates for GMP: dGMP [Spychala88 ]

In Pathways: purine nucleotides degradation II (aerobic) , guanosine nucleotides degradation III

Enzymatic reaction of: IMP 5'-nucleotidase (cytosolic 5'-nucleotidase II)

IMP[periplasmic space] + H2O[periplasmic space] <=> inosine[periplasmic space] + phosphate[periplasmic space]

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is favored in the direction shown.

Alternative Substrates for IMP: GMP [Spychala88 ] , dGMP [Spychala88 ] , XMP [Spychala88 ] , dIMP [Spychala88 ]

The native enzyme has been purified to homogeneity from human placenta and characterized. It was most active with IMP, dIMP, GMP and dGMP and was much less active with AMP dAMP and pyrimidine nucleoside monophosphates. It required Mg2+, but Co2+ and Zn2+ could substitute at lower efficiency. It was allosterically activated by the purine nucleotide triphosphates dATP, ATP and GTP. ATP activation required Mg2+. It was also activated by 2,3-diphospho-D-glycerate. It was inhibited by phosphate. The enzyme appears to be regulated by IMP (substrate), ATP and phosphate levels. XMP is also a substrate for this enzyme [Spychala88].

Cofactors or Prosthetic Groups: Mg2+ [Spychala88], Zn2+ [Spychala88], Co2+ [Spychala88]

Activators (Allosteric): GTP [Spychala88] , dATP [Spychala88] , ATP [Spychala88] , 2,3-diphospho-D-glycerate [Spychala88]

Inhibitors (Unknown Mechanism): phosphate [Spychala88]

pH(opt): 6.5 [Spychala88]


Bianchi03: Bianchi V, Spychala J (2003). "Mammalian 5'-nucleotidases." J Biol Chem 278(47);46195-8. PMID: 12947102

Borowiec06: Borowiec A, Lechward K, Tkacz-Stachowska K, Skladanowski AC (2006). "Adenosine as a metabolic regulator of tissue function: production of adenosine by cytoplasmic 5'-nucleotidases." Acta Biochim Pol 53(2);269-78. PMID: 16770441

Hunsucker05: Hunsucker SA, Mitchell BS, Spychala J (2005). "The 5'-nucleotidases as regulators of nucleotide and drug metabolism." Pharmacol Ther 107(1);1-30. PMID: 15963349

Oka94: Oka J, Matsumoto A, Hosokawa Y, Inoue S (1994). "Molecular cloning of human cytosolic purine 5'-nucleotidase." Biochem Biophys Res Commun 205(1);917-22. PMID: 7999131

SalaNewby00: Sala-Newby GB, Freeman NV, Skladanowski AC, Newby AC (2000). "Distinct roles for recombinant cytosolic 5'-nucleotidase-I and -II in AMP and IMP catabolism in COS-7 and H9c2 rat myoblast cell lines." J Biol Chem 275(16);11666-71. PMID: 10766785

Spychala88: Spychala J, Madrid-Marina V, Fox IH (1988). "High Km soluble 5'-nucleotidase from human placenta. Properties and allosteric regulation by IMP and ATP." J Biol Chem 263(35);18759-65. PMID: 2848805

Wallden07: Wallden K, Stenmark P, Nyman T, Flodin S, Graslund S, Loppnau P, Bianchi V, Nordlund P (2007). "Crystal structure of human cytosolic 5'-nucleotidase II: insights into allosteric regulation and substrate recognition." J Biol Chem 282(24);17828-36. PMID: 17405878

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Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
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