Disease relevance of NT5C2

• cN-II expression predicts survival in patients receiving gemcitabine for advanced non-small cell lung cancer [1].
• In a multivariate analysis taking into account age, sex, weight loss, stage and immunohistochemical results, cN-II was the only predictive factor associated with overall survival [1].
• Crystal structures have been determined for free Escherichia coli hypoxanthine phosphoribosyltransferase (HPRT) (2.9 A resolution) and for the enzyme in complex with the reaction products, inosine 5'-monophosphate (IMP) and guanosine 5'-monophosphate (GMP) (2.8 A resolution) [2].
• It is proposed that lack of GMP for functions, other than its role in pterin de novo synthesis, accounts for the features of the Lesch-Nyhan syndrome which do not occur when only tetrahydrobiopterin production is deficient as in the inborn errors of tetrahydrobiopterin synthesis [3].
• Role of IMP-selective 5'-nucleotidase (cN-II) in hematological malignancies [4].

High impact information on NT5C2

• However, GMP-PNP vesicles fail to target and fuse with the Golgi complex whereas GTP vesicles are functional [5].
• This renders the parasite susceptible to inhibition of inosine monophosphate dehydrogenase, the rate-limiting enzyme in the multistep conversion of AMP to GMP [6].
• The complex, after purification by phosphocellulose chromatography, can transfer its bound GMP moiety to pyrophosphate, regenerating GTP, or to the 5'-diphosphate end of poly(A), forming a cap structure G(5')pppA(pA)n. The GMP-polypeptide has a molecular weight of 65,000 and is stable to heating in the presence of sodium dodecyl sulfate [7].
• Phosphoamide linkage of the GMP-enzyme complex was indicated by its sensitivity to cleavage by acidic hydroxylamine or HCl and not by NaOH or alkaline phosphatase [8].
• Growth inhibition by bredinin was prevented by guanosine 5'-monophosphate (GMP), guanosine, or guanine but not by other purine or pyrimidine nucleotides, nucleosides, or bases [9].

Chemical compound and disease context of NT5C2

• GCV-MP binds as GMP to the GMP-binding domain, which is identical in E. coli and human GMPKs, but unlike the natural substrate fails to stabilize the closed, catalytically-competent conformation of this domain [10].
• The most important purine nucleotides (NAD, AMP, IMP, GMP, XMP, ADP, ATP, GDP, GTP) were analyzed by HPLC in the lymphocytes of healthy subjects and HIV-1 seropositive patients at different stages of the disease (ARC-AIDS) [11].
• Inhibition by thio-GMP also seems to occur in patients treated with 6-mercaptopurine (6 MP); subsequently, this may lead to toxicity in these patients [12].
• In hyperthermia experiments a tumor-size-dependent, significant increase in the levels of the following catabolites has been demonstrated: [symbol: see text] [IMP + GMP] (sum of guanosine and inosine monophosphate levels), inosine, hypoxanthine, xanthine and uric acid, along with a drop in ATP and guanosine triphosphate (GTP) levels [13].

Biological context of NT5C2

• The deduced amino acid sequence exhibits 95% identity with the sequence of the B type subunit of chicken cytosolic purine 5'-nucleotidase [14].
• The cDNA of human cytosolic purine 5'-nucleotidase (EC 3.1.3.5), which is the supposed regulatory allosteric enzyme of purine nucleotide degradation, has been cloned from a human placenta cDNA library [14].
• Purine ribonucleotides produce sigmoidal kinetics with respect to the substrate PP-ribose-P, with Hill coefficients of 1.4 to 1.6 and 1.8 to 2.0 in the presence of AMP and GMP, respectively [15].
• Guanosine monophosphate kinases (GMPKs), which catalyze the phosphorylation of GMP and dGMP to their diphosphate form, have been characterized as monomeric enzymes in eukaryotes and prokaryotes [16].
• The capacity of intact synaptosomes to hydrolyze also extracellular ADP, GDP, AMP, GMP, and IMP suggests that the nucleoside triphosphatase is part of an enzyme chain that causes complete hydrolysis of the respective nucleoside triphosphate to the nucleoside [17].

Anatomical context of NT5C2

• In COS-7 cells, 5'-nucleotidase activity was not rate-limiting for inosine and hypoxanthine production, which was therefore unaffected by cN-II- and actually reduced by cN-I- overexpression [18].
• Inhibitors of GMP-dependent kinase and myosin L chain kinase had no effect on rMCAF-induced monocyte migration [19].
• It is concluded that the glycerate 2,3-bisphosphate-stimulated purine 5'-nucleotidase is responsible for the dephosphorylation of IMP and GMP, but not of AMP, in human erythrocytes [20].
• In conclusion, this study demonstrates that human eosinophils present a nitric oxide-cyclic GMP pathway that is involved in the in vitro locomotion of this cell type [21].
• The activity of high K(m) 5'-nucleotidase (5'-NT) (cN-II) using IMP as substrate, was 2-fold elevated in the resistant cell lines [22].

Associations of NT5C2 with chemical compounds

• Overexpression of certain nucleotidases, such as cN-II, has also been frequently shown in gemcitabine-resistant models [1].
• Inhibition by bredinin at a low GMP; but at higher concentrations of bredinin the inhibition was not reversed even when the concentration of GMP was raised [9].
• Evidence for the involvement of cytosolic 5'-nucleotidase (cN-II) in the synthesis of guanine nucleotides from xanthosine [23].
• In H9c2 cells, in which 5'-nucleotidase activity was rate-limiting, only cN-II overexpression accelerated inosine and hypoxanthine formation [18].
• Chemical reagents specifically modifying aspartate and glutamate residues inhibit the enzyme, and this inhibition is partially prevented by cN-II substrates and physiological inhibitors [24].
• The model shows why diadenosine tetraphosphate but not diadenosine triphosphate activates the enzyme and supports a role for cN-II during apoptosis when the level of diadenosine tetraphosphate increases [25].

Other interactions of NT5C2

• Among the 43 samples, only 7 (16%) expressed detectable hENT1, with a low percentage of positive cells, 18 expressed hCNT3 (42%), 36 (86%) expressed cN-II and 28 (66%) expressed dCK [1].
• Our results show that high mRNA levels of cN-II and low mRNA levels of cN-III are correlated with a worse clinical outcome and suggest that these enzymes may have a role in sensitivity to ara-C in AML patients [26].
• Deoxycytidine kinase and cN-II nucleotidase expression in blast cells predict survival in acute myeloid leukaemia patients treated with cytarabine [27].

Analytical, diagnostic and therapeutic context of NT5C2

• Molecular cloning of human cytosolic purine 5'-nucleotidase [14].
• Digestion of [7-(14)C]phenylglyoxal-modified enzyme with trypsin and separation of the peptides by reverse-phase HPLC shows that only one radioactive peak is greatly diminished by incubation with 25 microM GMP or 1 mM PRibPP [28].
• These investigations should contribute to the clarification of the controlling factors of GMP biosynthesis, the role of the various enzymes, the behavior of GMP reductase in mammalian cells and the application of the approaches of enzyme-pattern-targeted chemotherapy in patients [29].
• (8) The synergistic biological results of combination chemotherapy with acivicin and actinomycin can be accounted for by the action of acivicin in inhibiting GMP and CTP synthetases, resulting in a decrease in GTP and CTP content, and by the actinomycin-caused inhibition of RNA polymerase in selectively blocking the utilization of GTP and CTP [30].
• Second, the isolated complex was further characterized by Western blot analysis, the formation of a GMP-protein complex, and transcriptional activity [31].

References