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Purhonen J, Hofer A, Kallijärvi J. Quantification of all 12 canonical ribonucleotides by real-time fluorogenic in vitro transcription. Nucleic Acids Res 2024; 52:e6. [PMID: 38008466 PMCID: PMC10783517 DOI: 10.1093/nar/gkad1091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 10/17/2023] [Accepted: 10/30/2023] [Indexed: 11/28/2023] Open
Abstract
Enzymatic methods to quantify deoxyribonucleoside triphosphates have existed for decades. In contrast, no general enzymatic method to quantify ribonucleoside triphosphates (rNTPs), which drive almost all cellular processes and serve as precursors of RNA, exists to date. ATP can be measured with an enzymatic luminometric method employing firefly luciferase, but the quantification of other ribonucleoside mono-, di-, and triphosphates is still a challenge for a non-specialized laboratory and practically impossible without chromatography equipment. To allow feasible quantification of ribonucleoside phosphates in any laboratory with typical molecular biology and biochemistry tools, we developed a robust microplate assay based on real-time detection of the Broccoli RNA aptamer during in vitro transcription. The assay employs the bacteriophage T7 and SP6 RNA polymerases, two oligonucleotide templates encoding the 49-nucleotide Broccoli aptamer, and a high-affinity fluorogenic aptamer-binding dye to quantify each of the four canonical rNTPs. The inclusion of nucleoside mono- and diphosphate kinases in the assay reactions enabled the quantification of the mono- and diphosphate counterparts. The assay is inherently specific and tolerates concentrated tissue and cell extracts. In summary, we describe the first chromatography-free method to quantify ATP, ADP, AMP, GTP, GDP, GMP, UTP, UDP, UMP, CTP, CDP and CMP in biological samples.
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Affiliation(s)
- Janne Purhonen
- Folkhälsan Research Center, Helsinki 00290, Finland
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki 00014, Finland
| | - Anders Hofer
- Department of Medical Biochemistry and Biophysics, Umeå University, Umeå 90187, Sweden
| | - Jukka Kallijärvi
- Folkhälsan Research Center, Helsinki 00290, Finland
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki 00014, Finland
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Chen M, Luo J, Jiang W, Chen L, Miao L, Han C. Cordycepin: A review of strategies to improve the bioavailability and efficacy. Phytother Res 2023; 37:3839-3858. [PMID: 37329165 DOI: 10.1002/ptr.7921] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 05/24/2023] [Accepted: 05/27/2023] [Indexed: 06/18/2023]
Abstract
Cordycepin is a bioactive compound extracted from Cordyceps militaris. As a natural antibiotic, cordycepin has a wide variety of pharmacological effects. Unfortunately, this highly effective natural antibiotic is proved to undergo rapid deamination by adenosine deaminase (ADA) in vivo and, as a consequence, its half-life is shortened and bioavailability is decreased. Therefore, it is of critical importance to work out ways to slow down the deamination so as to increase its bioavailability and efficacy. This study reviews recent researches on a series of aspects of cordycepin such as the bioactive molecule's pharmacological action, metabolism and transformation as well as the underlying mechanism, pharmacokinetics and, particularly, the methods for reducing the degradation to improve the bioavailability and efficacy. It is drawn that there are three methods that can be applied to improve the bioavailability and efficacy: to co-administrate an ADA inhibitor and cordycepin, to develop more effective derivatives via structural modification, and to apply new drug delivery systems. The new knowledge can help optimize the application of the highly potent natural antibiotic-cordycepin and develop novel therapeutic strategies.
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Affiliation(s)
- Min Chen
- School of Pharmacy, Shandong University of Traditional Chinese Medicine, Jinan, China
- School of Medicine, Linyi University, Linyi, China
| | - Jiahao Luo
- School of Pharmacy, Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Wenming Jiang
- School of Pharmacy, Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Lijing Chen
- School of Pharmacy, Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Longxing Miao
- School of Pharmacy, Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Chunchao Han
- School of Pharmacy, Shandong University of Traditional Chinese Medicine, Jinan, China
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3
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Moschini R, Balestri F, Cappiello M, Signore G, Mura U, Del-Corso A. Ribose Intake as Food Integrator: Is It a Really Convenient Practice? Biomolecules 2022; 12:biom12121775. [PMID: 36551203 PMCID: PMC9776227 DOI: 10.3390/biom12121775] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Revised: 11/07/2022] [Accepted: 11/22/2022] [Indexed: 12/02/2022] Open
Abstract
Reports concerning the beneficial effects of D-ribose administration in cardiovascular and muscle stressful conditions has led to suggestions for the use of ribose as an energizing food supplement for healthy people. However, this practice still presents too many critical issues, suggesting that caution is needed. In fact, there are many possible negative effects of this sugar that we believe are underestimated, if not neglected, by the literature supporting the presentation of the product to the market. Here, the risks deriving from the use of free ribose as ATP source, forcing ribose-5-phosphate to enter into the pentose phosphate pathway, is emphasized. On the basis of the remarkable glycation capacity of ribose, the easily predictable cytotoxic effect of the molecule is also highlighted.
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Affiliation(s)
- Roberta Moschini
- Biochemistry Unit, Department of Biology, University of Pisa, Via San Zeno, 51, 56127 Pisa, Italy
- Interdepartmental Research Center Nutrafood “Nutraceuticals and Food for Health”, University of Pisa, 56124 Pisa, Italy
| | - Francesco Balestri
- Biochemistry Unit, Department of Biology, University of Pisa, Via San Zeno, 51, 56127 Pisa, Italy
- Interdepartmental Research Center Nutrafood “Nutraceuticals and Food for Health”, University of Pisa, 56124 Pisa, Italy
| | - Mario Cappiello
- Biochemistry Unit, Department of Biology, University of Pisa, Via San Zeno, 51, 56127 Pisa, Italy
- Interdepartmental Research Center Nutrafood “Nutraceuticals and Food for Health”, University of Pisa, 56124 Pisa, Italy
| | - Giovanni Signore
- Biochemistry Unit, Department of Biology, University of Pisa, Via San Zeno, 51, 56127 Pisa, Italy
- Interdepartmental Research Center Nutrafood “Nutraceuticals and Food for Health”, University of Pisa, 56124 Pisa, Italy
| | - Umberto Mura
- Biochemistry Unit, Department of Biology, University of Pisa, Via San Zeno, 51, 56127 Pisa, Italy
- Correspondence:
| | - Antonella Del-Corso
- Biochemistry Unit, Department of Biology, University of Pisa, Via San Zeno, 51, 56127 Pisa, Italy
- Interdepartmental Research Center Nutrafood “Nutraceuticals and Food for Health”, University of Pisa, 56124 Pisa, Italy
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Liang L, Yang LL, Wang W, Ji C, Zhang L, Jia Y, Chen Y, Wang X, Tan J, Sun ZJ, Yuan Q, Tan W. Calcium Phosphate-Reinforced Metal-Organic Frameworks Regulate Adenosine-Mediated Immunosuppression. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2102271. [PMID: 34554618 DOI: 10.1002/adma.202102271] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Revised: 07/26/2021] [Indexed: 05/26/2023]
Abstract
Long-term accumulation of adenosine (Ado) in tumor tissues helps to establish the immunosuppressive tumor microenvironment and to promote tumor development. Regulation of Ado metabolism is particularly pivotal for blocking Ado-mediated immunosuppression. The activity of adenosine kinase (ADK) for catalyzing the phosphorylation of Ado plays an essential role in regulating Ado metabolism. Specifically, accumulated Ado in the tumor microenvironment occupies the active site of ADK, inhibiting the phosphorylation of Ado. Phosphate can protect ADK from inactivation and restore the activity of ADK. Herein, calcium phosphate-reinforced iron-based metal-organic frameworks (CaP@Fe-MOFs) are designed to reduce Ado accumulation and to inhibit Ado-mediated immunosuppressive response in the tumor microenvironment. CaP@Fe-MOFs are found to regulate the Ado metabolism by promoting ADK-mediated phosphorylation and relieving the hypoxic tumor microenvironment. Moreover, CaP@Fe-MOFs can enhance the antitumor immune response via Ado regulation, including the increase of T lymphocytes and dendritic cells and the decrease of regulatory T lymphocytes. Finally, CaP@Fe-MOFs are used for cancer treatment in mice, alleviating the Ado-mediated immunosuppressive response and achieving tumor suppression. This study may offer a general strategy for blocking the Ado-mediated immunosuppression in the tumor microenvironment and further for enhancing the immunotherapy efficacy in vivo.
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Affiliation(s)
- Ling Liang
- Institute of Chemical Biology and Nanomedicine, Molecular Science and Biomedicine Laboratory, State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, China
| | - Lei-Lei Yang
- The State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST) and Key Laboratory of Oral Biomedicine Ministry of Education, School and Hospital of Stomatology, College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, 430072, China
| | - Wenjie Wang
- Institute of Chemical Biology and Nanomedicine, Molecular Science and Biomedicine Laboratory, State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, China
| | - Cailing Ji
- Institute of Chemical Biology and Nanomedicine, Molecular Science and Biomedicine Laboratory, State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, China
| | - Lei Zhang
- Institute of Chemical Biology and Nanomedicine, Molecular Science and Biomedicine Laboratory, State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, China
| | - Yiyi Jia
- Institute of Chemical Biology and Nanomedicine, Molecular Science and Biomedicine Laboratory, State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, China
| | - Yuxia Chen
- Institute of Chemical Biology and Nanomedicine, Molecular Science and Biomedicine Laboratory, State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, China
| | - Xueqiang Wang
- Institute of Chemical Biology and Nanomedicine, Molecular Science and Biomedicine Laboratory, State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, China
| | - Jie Tan
- Institute of Chemical Biology and Nanomedicine, Molecular Science and Biomedicine Laboratory, State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, China
| | - Zhi-Jun Sun
- The State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST) and Key Laboratory of Oral Biomedicine Ministry of Education, School and Hospital of Stomatology, College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, 430072, China
| | - Quan Yuan
- Institute of Chemical Biology and Nanomedicine, Molecular Science and Biomedicine Laboratory, State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, China
- The State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST) and Key Laboratory of Oral Biomedicine Ministry of Education, School and Hospital of Stomatology, College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, 430072, China
| | - Weihong Tan
- Institute of Chemical Biology and Nanomedicine, Molecular Science and Biomedicine Laboratory, State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, China
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Hellendahl KF, Fehlau M, Hans S, Neubauer P, Kurreck A. Semi-Automated High-Throughput Substrate Screening Assay for Nucleoside Kinases. Int J Mol Sci 2021; 22:11558. [PMID: 34768989 PMCID: PMC8584170 DOI: 10.3390/ijms222111558] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 10/18/2021] [Accepted: 10/20/2021] [Indexed: 11/21/2022] Open
Abstract
Nucleoside kinases (NKs) are key enzymes involved in the in vivo phosphorylation of nucleoside analogues used as drugs to treat cancer or viral infections. Having different specificities, the characterization of NKs is essential for drug design and nucleotide analogue production in an in vitro enzymatic process. Therefore, a fast and reliable substrate screening method for NKs is of great importance. Here, we report on the validation of a well-known luciferase-based assay for the detection of NK activity in a 96-well plate format. The assay was semi-automated using a liquid handling robot. Good linearity was demonstrated (r² > 0.98) in the range of 0-500 µM ATP, and it was shown that alternative phosphate donors like dATP or CTP were also accepted by the luciferase. The developed high-throughput assay revealed comparable results to HPLC analysis. The assay was exemplarily used for the comparison of the substrate spectra of four NKs using 20 (8 natural, 12 modified) substrates. The screening results correlated well with literature data, and additionally, previously unknown substrates were identified for three of the NKs studied. Our results demonstrate that the developed semi-automated high-throughput assay is suitable to identify best performing NKs for a wide range of substrates.
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Affiliation(s)
- Katja F. Hellendahl
- Chair of Bioprocess Engineering, Faculty III Process Sciences, Institute of Biotechnology, Technische Universität Berlin, Ackerstraße 76, 13355 Berlin, Germany; (K.F.H.); (M.F.); (S.H.); (P.N.)
| | - Maryke Fehlau
- Chair of Bioprocess Engineering, Faculty III Process Sciences, Institute of Biotechnology, Technische Universität Berlin, Ackerstraße 76, 13355 Berlin, Germany; (K.F.H.); (M.F.); (S.H.); (P.N.)
- BioNukleo GmbH, Ackerstraße 76, 13355 Berlin, Germany
| | - Sebastian Hans
- Chair of Bioprocess Engineering, Faculty III Process Sciences, Institute of Biotechnology, Technische Universität Berlin, Ackerstraße 76, 13355 Berlin, Germany; (K.F.H.); (M.F.); (S.H.); (P.N.)
| | - Peter Neubauer
- Chair of Bioprocess Engineering, Faculty III Process Sciences, Institute of Biotechnology, Technische Universität Berlin, Ackerstraße 76, 13355 Berlin, Germany; (K.F.H.); (M.F.); (S.H.); (P.N.)
| | - Anke Kurreck
- Chair of Bioprocess Engineering, Faculty III Process Sciences, Institute of Biotechnology, Technische Universität Berlin, Ackerstraße 76, 13355 Berlin, Germany; (K.F.H.); (M.F.); (S.H.); (P.N.)
- BioNukleo GmbH, Ackerstraße 76, 13355 Berlin, Germany
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6
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Ribeiro D, Planchon S, Leclercq C, Raundrup K, Alves S, Bessa R, Renaut J, Almeida A. The muscular, hepatic and adipose tissues proteomes in muskox (Ovibos moschatus): Differences between males and females. J Proteomics 2019; 208:103480. [DOI: 10.1016/j.jprot.2019.103480] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Revised: 07/28/2019] [Accepted: 08/02/2019] [Indexed: 02/07/2023]
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Abstract
Adenosine kinase (ADK; EC 2.7.1.20) is an evolutionarily conserved phosphotransferase that converts the purine ribonucleoside adenosine into 5'-adenosine-monophosphate. This enzymatic reaction plays a fundamental role in determining the tone of adenosine, which fulfills essential functions as a homeostatic and metabolic regulator in all living systems. Adenosine not only activates specific signaling pathways by activation of four types of adenosine receptors but it is also a primordial metabolite and regulator of biochemical enzyme reactions that couple to bioenergetic and epigenetic functions. By regulating adenosine, ADK can thus be identified as an upstream regulator of complex homeostatic and metabolic networks. Not surprisingly, ADK dysfunction is involved in several pathologies, including diabetes, epilepsy, and cancer. Consequently, ADK emerges as a rational therapeutic target, and adenosine-regulating drugs have been tested extensively. In recent attempts to improve specificity of treatment, localized therapies have been developed to augment adenosine signaling at sites of injury or pathology; those approaches include transplantation of stem cells with deletions of ADK or the use of gene therapy vectors to downregulate ADK expression. More recently, the first human mutations in ADK have been described, and novel findings suggest an unexpected role of ADK in a wider range of pathologies. ADK-regulating strategies thus represent innovative therapeutic opportunities to reconstruct network homeostasis in a multitude of conditions. This review will provide a comprehensive overview of the genetics, biochemistry, and pharmacology of ADK and will then focus on pathologies and therapeutic interventions. Challenges to translate ADK-based therapies into clinical use will be discussed critically.
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Affiliation(s)
- Detlev Boison
- Legacy Research Institute, 1225 NE 16th Ave, Portland, OR 97202, USA.
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8
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Elkin SR, Kumar A, Price CW, Columbus L. A broad specificity nucleoside kinase from Thermoplasma acidophilum. Proteins 2013; 81:568-82. [PMID: 23161756 DOI: 10.1002/prot.24212] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Revised: 10/18/2012] [Accepted: 11/01/2012] [Indexed: 11/07/2022]
Abstract
The crystal structure of Ta0880, determined at 1.91 Å resolution, from Thermoplasma acidophilum revealed a dimer with each monomer composed of an α/β/α sandwich domain and a smaller lid domain. The overall fold belongs to the PfkB family of carbohydrate kinases (a family member of the Ribokinase clan) which include ribokinases, 1-phosphofructokinases, 6-phosphofructo-2-kinase, inosine/guanosine kinases, fructokinases, adenosine kinases, and many more. Based on its general fold, Ta0880 had been annotated as a ribokinase-like protein. Using a coupled pyruvate kinase/lactate dehydrogenase assay, the activity of Ta0880 was assessed against a variety of ribokinase/pfkB-like family substrates; activity was not observed for ribose, fructose-1-phosphate, or fructose-6-phosphate. Based on structural similarity with nucleoside kinases (NK) from Methanocaldococcus jannaschii (MjNK, PDB 2C49, and 2C4E) and Burkholderia thailandensis (BtNK, PDB 3B1O), nucleoside kinase activity was investigated. Ta0880 (TaNK) was confirmed to have nucleoside kinase activity with an apparent KM for guanosine of 0.21 μM and catalytic efficiency of 345,000 M(-1) s(-1) . These three NKs have significantly different substrate, phosphate donor, and cation specificities and comparisons of specificity and structure identified residues likely responsible for the nucleoside substrate selectivity. Phylogenetic analysis identified three clusters within the PfkB family and indicates that TaNK is a member of a new sub-family with broad nucleoside specificities. Proteins 2013. © 2012 Wiley Periodicals, Inc.
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Affiliation(s)
- Sarah R Elkin
- Department of Chemistry, University of Virginia, Charlottesville, VA 22904-4319, USA
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Romanello L, Bachega JFR, Cassago A, Brandão-Neto J, DeMarco R, Garratt RC, Pereira HD. Adenosine kinase from Schistosoma mansoni: structural basis for the differential incorporation of nucleoside analogues. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2012; 69:126-36. [PMID: 23275171 DOI: 10.1107/s0907444912044800] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Accepted: 10/29/2012] [Indexed: 11/10/2022]
Abstract
In adult schistosomes, the enzyme adenosine kinase (AK) is responsible for the incorporation of some adenosine analogues, such as 2-fluoroadenosine and tubercidin, into the nucleotide pool, but not others. In the present study, the structures of four complexes of Schistosoma mansoni AK bound to adenosine and adenosine analogues are reported which shed light on this observation. Two differences in the adenosine-binding site in comparison with the human counterpart (I38Q and T36A) are responsible for their differential specificities towards adenosine analogues, in which the Schistosoma enzyme does not tolerate bulky substituents at the N7 base position. This aids in explaining experimental data which were reported in the literature more than two decades ago. Furthermore, there appears to be considerable plasticity within the substrate-binding sites that affects the side-chain conformation of Ile38 and causes a previously unobserved flexibility within the loop comprising residues 286-299. These results reveal that the latter can be sterically occluded in the absence of ATP. Overall, these results contribute to the body of knowledge concerning the enzymes of the purine salvage pathway in this important human parasite.
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Affiliation(s)
- Larissa Romanello
- Centro de Biotecnologia Molecular Estrutural, Instituto de Física de São Carlos, Universidade de São Paulo, Brazil
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Bjursell M, Blom H, Cayuela J, Engvall M, Lesko N, Balasubramaniam S, Brandberg G, Halldin M, Falkenberg M, Jakobs C, Smith D, Struys E, von Döbeln U, Gustafsson C, Lundeberg J, Wedell A. Adenosine kinase deficiency disrupts the methionine cycle and causes hypermethioninemia, encephalopathy, and abnormal liver function. Am J Hum Genet 2011; 89:507-15. [PMID: 21963049 DOI: 10.1016/j.ajhg.2011.09.004] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Revised: 09/06/2011] [Accepted: 09/07/2011] [Indexed: 10/17/2022] Open
Abstract
Four inborn errors of metabolism (IEMs) are known to cause hypermethioninemia by directly interfering with the methionine cycle. Hypermethioninemia is occasionally discovered incidentally, but it is often disregarded as an unspecific finding, particularly if liver disease is involved. In many individuals the hypermethioninemia resolves without further deterioration, but it can also represent an early sign of a severe, progressive neurodevelopmental disorder. Further investigation of unclear hypermethioninemia is therefore important. We studied two siblings affected by severe developmental delay and liver dysfunction. Biochemical analysis revealed increased plasma levels of methionine, S-adenosylmethionine (AdoMet), and S-adenosylhomocysteine (AdoHcy) but normal or mildly elevated homocysteine (Hcy) levels, indicating a block in the methionine cycle. We excluded S-adenosylhomocysteine hydrolase (SAHH) deficiency, which causes a similar biochemical phenotype, by using genetic and biochemical techniques and hypothesized that there was a functional block in the SAHH enzyme as a result of a recessive mutation in a different gene. Using exome sequencing, we identified a homozygous c.902C>A (p.Ala301Glu) missense mutation in the adenosine kinase gene (ADK), the function of which fits perfectly with this hypothesis. Increased urinary adenosine excretion confirmed ADK deficiency in the siblings. Four additional individuals from two unrelated families with a similar presentation were identified and shown to have a homozygous c.653A>C (p.Asp218Ala) and c.38G>A (p.Gly13Glu) mutation, respectively, in the same gene. All three missense mutations were deleterious, as shown by activity measurements on recombinant enzymes. ADK deficiency is a previously undescribed, severe IEM shedding light on a functional link between the methionine cycle and adenosine metabolism.
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Nishino T, Yachie-Kinoshita A, Hirayama A, Soga T, Suematsu M, Tomita M. In silico modeling and metabolome analysis of long-stored erythrocytes to improve blood storage methods. J Biotechnol 2009; 144:212-23. [PMID: 19695295 DOI: 10.1016/j.jbiotec.2009.08.010] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2009] [Revised: 08/03/2009] [Accepted: 08/07/2009] [Indexed: 11/30/2022]
Abstract
There is currently no effective method for preventing ATP and 2,3-bisphosphoglycerate (2,3-BPG) depletion during long-term erythrocyte storage in the cold, although these metabolites are strongly associated with cell viability and oxygen delivery after transfusion. Metabolite reduction is caused by whole metabolic networks in the cell, which are regulated by various physical or chemical factors. Mathematical modeling is a powerful tool for integrating such complex and dynamic systems. Here, we developed a mathematical model to predict metabolism in erythrocytes preserved with a mannitol-adenine-phosphate solution (MAP) at 4 degrees C, by modifying a published model of large-scale erythrocyte metabolism. Our model successfully reproduced the reported decreases in ATP and 2,3-BPG during storage. Analysis of our model identified several enzymatic reactions and factors related to ATP and 2,3-BPG depletions, which may serve as possible targets for improving blood storage methods. We also performed metabolome analysis of laboratory-made MAP-stored erythrocytes using capillary electrophoresis time-of-flight mass spectrometry (CE-TOFMS), which provided a comprehensive view of the metabolism dynamics. Alterations in the metabolic intermediate concentrations after long storage were qualitatively predicted by the model. Finally, through further systematic analysis, we also discuss the usability of our model.
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Affiliation(s)
- Taiko Nishino
- Institute for Advanced Biosciences, Keio University, 403-1, Daihoji, Tsuruoka, Yamagata 997-0017, Japan
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12
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Ota H, Sakasegawa SI, Yasuda Y, Imamura S, Tamura T. A novel nucleoside kinase from Burkholderia thailandensis: a member of the phosphofructokinase B-type family of enzymes. FEBS J 2009; 275:5865-72. [PMID: 19021762 DOI: 10.1111/j.1742-4658.2008.06716.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The genome of the mesophilic Gram-negative bacterium Burkholderia thailandensis contains an open reading frame (i.e. the Bth_I1158 gene) that has been annotated as a putative ribokinase and PFK-B family member. Notably, although the deduced amino acid sequence of the gene showed only 29% similarity to the recently identified nucleoside kinase from hyperthermophilic archaea Methanocaldococcus jannaschii, 15 of 17 residues reportedly involved in the catalytic activity of M. jannaschii nucleoside kinase were conserved. The gene was cloned and functionally overexpressed in Rhodococcus erythropolis, and the purified enzyme was characterized biochemically. The substrate specificity of the enzyme was unusually broad for a bacterial PFK-B protein, and the specificity extended not only to purine and purine-analog nucleosides but also to uridine. Inosine was the most effective phosphoryl acceptor, with the highest k(cat)/K(m) value (80 s(-1).mm(-1)) being achieved when ATP served as the phosphoryl donor. By contrast, this enzyme exhibited no activity toward ribose, indicating that the recombinant enzyme was a nucleoside kinase rather than a ribokinase. To our knowledge, this is the first detailed analysis of a bacterial nucleoside kinase in the PFK-B family.
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Affiliation(s)
- Hiroko Ota
- Asahi Kasei Pharma Corporation, Shizuoka, Japan
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13
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Vannoni D, Giglioni S, Santoro A, Aceto E, Marinello E, Leoncini R. A kinetic study of the rat liver adenosine kinase reverse reaction. NUCLEOSIDES NUCLEOTIDES & NUCLEIC ACIDS 2008; 27:872-5. [PMID: 18600555 DOI: 10.1080/15257770802146544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Adenosine kinase is an enzyme catalyzing the reaction: adenosine + ATP --> AMP + ADP. We studied some biochemical properties not hitherto investigated and demonstrated that the reaction can be easily reversed when coupled with adenosine deaminase, which transforms adenosine into inosine and ammonia. The overall reaction is: AMP + ADP --> ATP + inosine + NH(3). The exoergonic ADA reaction shifts the equilibrium and fills the energy gap necessary for synthesis of ATP. This reaction could be used by cells under particular conditions of energy deficiency and, together with myokinase activity, may help to restore physiological ATP levels.
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Affiliation(s)
- D Vannoni
- Dipartimento di Medicina Interna, Sc. Endocrino-Metaboliche e Biochimica, Università di Siena, Siena, Italy.
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Leoncini R, Vannoni D, Santoro A, Giglioni S, Carli R, Marinello E. Adenosine kinase from rat liver: new biochemical properties. NUCLEOSIDES NUCLEOTIDES & NUCLEIC ACIDS 2007; 25:1107-12. [PMID: 17065073 DOI: 10.1080/15257770600894139] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Adenosine kinase is a well-known enzyme which catalyzes the phosphorylation of adenosine to AMP: Its metabolic and kinetic properties are well studied. Here, we report new properties of rat liver enzyme, demonstrating a new reaction: ADP can be a phosphate donor instead ATP, according to the reaction: adenosine + ADP --> 2AMP) demonstrating the efficiency of AdK to phosphorylate adenosine, also starting from ADP. Cells could exploited this property in situations in which ATP levels are strongly decreased and ADP decreases slowly.
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Affiliation(s)
- R Leoncini
- Department of Internal Medicine, Endocrine-Metabolic Sciences and Biochemistry University of Siena, Siena, Italy
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15
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Otsuguro KI, Yamaji Y, Ban M, Ohta T, Ito S. Involvement of adenosine in depression of synaptic transmission during hypercapnia in isolated spinal cord of neonatal rats. J Physiol 2006; 574:835-47. [PMID: 16740614 PMCID: PMC1817731 DOI: 10.1113/jphysiol.2006.109660] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Adenosine is one of the most important neuromodulators in the CNS, both under physiological and pathological conditions. In the isolated spinal cord of the neonatal rat in vitro, acute hypercapnic acidosis (20% CO2, pH 6.7) reversibly depressed electrically evoked spinal reflex potentials. This depression was partially reversed by 8-cyclopentlyl-1,3-dimethylxanthine (CPT), a selective A1 adenosine receptor antagonist. Isohydric hypercapnia (20% CO2, pH 7.3), but not isocapnic acidosis (5% CO2, pH 6.7), depressed the reflex potentials, which were also reversed by CPT. An ecto-5'-nucleotidase inhibitor did not affect the hypercapnic acidosis-evoked depression. An inhibitor of adenosine kinase, but not deaminase, mimicked the inhibitory effect of hypercapnic acidosis on the spinal reflex potentials. Accumulation of extracellular adenosine and inhibition of adenosine kinase activity were caused by hypercapnic acidosis and isohydric hypercapnia, but not isohydric acidosis. These results indicate that the activation of adenosine A1 receptors is involved in the hypercapnia-evoked depression of reflex potentials in the isolated spinal cord of the neonatal rat. The inhibition of adenosine kinase activity is suggested to cause the accumulation of extracellular adenosine during hypercapnia.
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Affiliation(s)
- Ken-ichi Otsuguro
- Laboratory of Pharmacology, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan.
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Wang Y, Long MC, Ranganathan S, Escuyer V, Parker WB, Li R. Overexpression, purification and crystallographic analysis of a unique adenosine kinase from Mycobacterium tuberculosis. Acta Crystallogr Sect F Struct Biol Cryst Commun 2005; 61:553-7. [PMID: 16511094 PMCID: PMC1952321 DOI: 10.1107/s1744309105013473] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2004] [Accepted: 04/27/2005] [Indexed: 11/10/2022]
Abstract
Adenosine kinase from Mycobacterium tuberculosis is the only prokaryotic adenosine kinase that has been isolated and characterized. The enzyme catalyzes the phosphorylation of adenosine to adenosine monophosphate and is involved in the activation of 2-methyladenosine, a compound that has demonstrated selective activity against M. tuberculosis. The mechanism of action of 2-methyladenosine is likely to be different from those of current tuberculosis treatments and this compound (or other adenosine analogs) may prove to be a novel therapeutic intervention for this disease. The M. tuberculosis adenosine kinase was overexpressed in Escherichia coli and the enzyme was purified with activity comparable to that reported previously. The protein was crystallized in the presence of adenosine using the vapour-diffusion method. The crystals diffracted X-rays to high resolution and a complete data set was collected to 2.2 A using synchrotron radiation. The crystal belonged to space group P3(1)21, with unit-cell parameters a = 70.2, c = 111.6 A, and contained a single protein molecule in the asymmetric unit. An initial structural model of the protein was obtained by the molecular-replacement method, which revealed a dimeric structure. The monomers of the dimer were related by twofold crystallographic symmetry. An understanding of how the M. tuberculosis adenosine kinase differs from the human homolog should aid in the design of more potent and selective antimycobacterial agents that are selectively activated by this enzyme.
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Affiliation(s)
- Yimin Wang
- Southern Research Institute, 2000 Ninth Avenue South, Birmingham, Alabama 35205, USA
| | - Mary C. Long
- Southern Research Institute, 2000 Ninth Avenue South, Birmingham, Alabama 35205, USA
| | - Senthil Ranganathan
- Southern Research Institute, 2000 Ninth Avenue South, Birmingham, Alabama 35205, USA
| | - Vincent Escuyer
- Southern Research Institute, 2000 Ninth Avenue South, Birmingham, Alabama 35205, USA
| | - William B. Parker
- Southern Research Institute, 2000 Ninth Avenue South, Birmingham, Alabama 35205, USA
| | - Rongbao Li
- Southern Research Institute, 2000 Ninth Avenue South, Birmingham, Alabama 35205, USA
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Abstract
Thirty years after its synthesis, the mechanism of action of ribavirin is still not completely understood. Although much is known about the metabolism and biochemical effects of ribavirin in human cells, there is still much to be learned about the precise mechanism of action of ribavirin with the various viruses. New information about its ability to induce mutations in viral genomes has led to new questions about its mechanism of action. There is considerable evidence that indicates that ribavirin triphosphate (RTP) can interact with the various viral RNA polymerases, and it seems likely that this interaction is important to the mechanism of action of ribavirin. It seems likely that ribavirin will not have one universal mechanism of action, but will inhibit different viruses in different ways. In some cases, inhibition of IMP dehydrogenase may be sufficient for antiviral activity. Whereas, in other cases, inhibition of viral RNA polymerases by RTP may be more important. It is also likely that RTP will interact with the different viral RNA polymerases in different ways leading to different mechanisms of actions. More comprehensive studies are needed that address all aspects of ribavirin metabolism and biochemical actions to gain a thorough understanding of the activity of this agent. Finally, the differences in the metabolism and biochemical actions of ribavirin, selenazofurin, and tiazofurin indicate that small structural changes can have profound effects on biological activity. This observation is well known by investigators familiar with nucleoside analogs, but indicate that one should not assume that agents of similar structure have identical activities.
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Affiliation(s)
- William B Parker
- Southern Research Institute, 2000 Ninth Avenue South, Birmingham, AL 35205, USA.
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Long MC, Escuyer V, Parker WB. Identification and characterization of a unique adenosine kinase from Mycobacterium tuberculosis. J Bacteriol 2003; 185:6548-55. [PMID: 14594827 PMCID: PMC262096 DOI: 10.1128/jb.185.22.6548-6555.2003] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Adenosine kinase (AK) is a purine salvage enzyme that catalyzes the phosphorylation of adenosine to AMP. In Mycobacterium tuberculosis, AK can also catalyze the phosphorylation of the adenosine analog 2-methyladenosine (methyl-Ado), the first step in the metabolism of this compound to an active form. Purification of AK from M. tuberculosis yielded a 35-kDa protein that existed as a dimer in its native form. Adenosine (Ado) was preferred as a substrate at least 30-fold (Km = 0.8 +/- 0.08 microM) over other natural nucleosides, and substrate inhibition was observed when Ado concentrations exceeded 5 micro M. M. tuberculosis and human AKs exhibited different affinities for methyl-Ado, with Km values of 79 and 960 microM, respectively, indicating that differences exist between the substrate binding sites of these enzymes. ATP was a good phosphate donor (Km = 1100 +/- 140 microM); however, the activity levels observed with dGTP and GTP were 4.7 and 2.5 times the levels observed with ATP, respectively. M. tuberculosis AK activity was dependent on Mg2+, and activity was stimulated by potassium, as reflected by a decrease in the Km and an increase in Vmax for both Ado and methyl-Ado. The N-terminal amino acid sequence of the purified enzyme revealed complete identity with Rv2202c, a protein currently classified as a hypothetical sugar kinase. When an AK-deficient strain of M. tuberculosis (SRICK1) was transformed with this gene, it exhibited a 5,000-fold increase in AK activity compared to extracts from the original mutants. These results verified that the protein that we identified as AK was coded for by Rv2202c. AK is not commonly found in bacteria, and to the best of our knowledge, M. tuberculosis AK is the first bacterial AK to be characterized. The enzyme shows greater sequence homology with ribokinase and fructokinase than it does with other AKs. The multiple differences that exist between M. tuberculosis and human AKs may provide the molecular basis for the development of nucleoside analog compounds with selective activity against M. tuberculosis.
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Affiliation(s)
- Mary C Long
- Southern Research Institute, Birmingham, Alabama 35205, USA
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Van Rompay AR, Johansson M, Karlsson A. Substrate specificity and phosphorylation of antiviral and anticancer nucleoside analogues by human deoxyribonucleoside kinases and ribonucleoside kinases. Pharmacol Ther 2003; 100:119-39. [PMID: 14609716 PMCID: PMC7126524 DOI: 10.1016/j.pharmthera.2003.07.001] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Structural analogues of nucleosides, nucleoside analogues (NA), are used in the treatment of cancer and viral infections. Antiviral NAs inhibit replication of the viral genome, whereas anticancer NAs inhibit cellular DNA replication and repair. NAs are inactive prodrugs that are dependent on intracellular phosphorylation to their pharmacologically active triphosphate form. The deoxyribonucleoside kinases (dNK) and ribonucleoside kinases (rNK) catalyze the first phosphorylation step, converting deoxyribonucleosides and ribonucleosides to their corresponding monophosphate form. The dNKs have been studied intensively, whereas the rNKs have not been as thoroughly investigated. This overview is focused on the substrate specificity, tissue distribution, and subcellular location of the mammalian dNKs and rNKs and their role in the activation of NAs.
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Key Words
- antiviral therapy
- anticancer therapy
- chemotherapy
- nucleoside analogue
- deoxyribonucleoside kinase
- ribonucleoside kinase
- adk, adenosine kinase
- aids, aquired immunodeficiency syndrome
- arac, 1-β-d-arabinofuranosylcytosine (cytarabine)
- arag, 9-β-d-arabinofuranosylguanine (nelarabine)
- azt, 3′-azido-2′,3′-dideoxythymidine (zidovudine)
- cafda, 2-chloro-2′-fluoro-9-β-d-arabinofuranosyladenine (clofarabine)
- cda, 2-chloro-2′-deoxyadenosine (cladribine)
- dck, deoxycytidine kinase
- ddc, 2′,3′-dideoxycytidine (zalcitabine)
- ddi, 2′,3′-dideoxyinosine (didanosine)
- dgk, deoxyguanosine kinase
- dfdc, 2′,2′-difluorodeoxycytidine (gemcitabine)
- dnk, deoxyribonucleoside kinase
- d4t, 2′,3′-didehydro-3′-deoxythymidine (stavudine)
- f-araa, 2-fluoro-9-β-d-arabinofuranosyladenine (fludarabine)
- fda, food and drug administration
- fiau, 1-(2′-deoxy-2′-fluoro-β-d-arabinofuranosyl)-5-iodouracil (fialuridine)
- hbv, hepatitis b virus
- mtdna, mitochondrial dna
- hiv, human immunodeficiency virus
- na, nucleoside analogue
- ndpk, nucleoside diphosphate kinase
- nmpk, nucleoside monophosphate kinase
- 5′-nt, 5′-nucleotidase
- rnk, ribonucleoside kinase
- rr, ribonucleotide reductase
- rt, reverse transcriptase
- tk1, thymidine kinase 1
- tk2, thymidine kinase 2
- uck1, uridine-cytidine kinase 1
- uck2, uridine-cytidine kinase 2
- 3tc, 2′-deoxy-3′-thiacytidine (lamivudine)
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Affiliation(s)
- An R Van Rompay
- Department of Nephrology-Hypertension, University of Antwerp, 2610 Antwerp, Belgium
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Mehl RA, Begley TP. Synthesis of32P-labeled intermediates on the purine biosynthetic pathway. J Labelled Comp Radiopharm 2002. [DOI: 10.1002/jlcr.627] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Pal S, Nair V. Phosphorylation of the anti-HIV compound (S,S)-isodideoxyadenosine by human recombinant deoxycytidine kinase. Biochem Pharmacol 2000; 60:1505-8. [PMID: 11020453 DOI: 10.1016/s0006-2952(00)00462-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
(S,S)-Isodideoxyadenosine [(S,S)-isoddA] is an anti-HIV active compound discovered in our laboratory. However, its cellular mechanism of action, particularly the critical first stage of phosphorylation, is not understood. IsoddA is not phosphorylated by adenosine kinase. Also, because it is not a substrate for adenosine deaminase, it would not be activated by the pathway taken by ddA, i. e. via 5'-nucleotidase phosphorylation of ddI and conversion of ddIMP to ddAMP. However, we have discovered that human recombinant 2'-deoxycytidine kinase (dCK) phosphorylates (S,S)-isoddA. The enzyme kinetic data revealed that the extent of monophosphorylation of this L-related nucleoside was comparable to that found with ddA. (S,S)-IsoddATP is among the most potent inhibitors of HIV reverse transcriptase known, which suggests that the observed low efficiency of phosphorylation of this compound by dCK is a key factor that limits the capacity of human lymphocytes to make (S,S)-isoddA an exceptionally active anti-HIV agent.
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Affiliation(s)
- S Pal
- Department of Chemistry, University of Iowa, Iowa City, IA 52242, USA
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22
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Pelicano H, Maury G, Elalaoui A, Shafiee M, Imbach JL, Goody RS, Divita G. Study of the substrate-binding properties of bovine liver adenosine kinase and inhibition by fluorescent nucleoside analogues. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 248:930-7. [PMID: 9342249 DOI: 10.1111/j.1432-1033.1997.00930.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Adenosine kinase (AK) catalyzes the phosphorylation of adenosine to AMP with ATP as phosphate donor. Intrinsic fluorescence of bovine liver AK was shown previously to be a sensitive probe to quantify the binding of substrates to the enzyme [Elaloui, A., Divita, G., Maury, G., Imbach, J.-L. & Goody, R. S. (1994) Eur. J Biochem. 221, 839-846]. AK contains two catalytic, sites: a high-affinity site, which binds adenosine and AMP selectively; and a site for ATP and ADP. In the present work, these two sites were characterized by combining the quenching of protein fluorescence induced by the binding of the ligands and the fluorescence enhancement observed upon binding of the N-methylanthraniloyl-derivated nucleotides or adenosine. A new fluorescent analog of adenosine, 5'-N-methylanthraniloyl-adenosine, was synthesized and shown to bind selectively to the high-affinity adenosine-binding site with an affinity similar to that of adenosine (Kd 1 microM). In contrast, 2'(3')-N-methylanthraniloyl derivatives of ATP, adenosine (5')tetraphospho(5')adenosine (Ap4A), and adenosine (5')pentaphospho(5')adenosine (Ap5A), bind to the enzyme at the ATP site. Methylantraniloyl derivatives of ATP and adenosine were used as tools for selective characterization of a series of adenosine analogues. The bisubstrate inhibitors Ap4A and Ap5A bind to the ATP site with high affinity and apparently not to the adenosine site, thus acting more as ATP analogues than true bisubstrate ligands. The binding properties of a series of adenosine analogues were strongly dependent on the structural modifications on adenosine. The analogues modified at positions 2' or 3' show similar affinities for AK as that of adenosine, whereas adenosine analogues modified at the base present a relatively low affinity for the enzyme.
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Affiliation(s)
- H Pelicano
- Université de Montpellier II Sciences et Techniques du Languedoc, URA 488 du CNRS, France
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McNally T, Helfrich RJ, Cowart M, Dorwin SA, Meuth JL, Idler KB, Klute KA, Simmer RL, Kowaluk EA, Halbert DN. Cloning and expression of the adenosine kinase gene from rat and human tissues. Biochem Biophys Res Commun 1997; 231:645-50. [PMID: 9070863 DOI: 10.1006/bbrc.1997.6157] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Adenosine kinase is ubiquitous in eukaryotes and is a key enzyme in the regulation of the intracellular levels of adenosine, an important physiological effector of many cells and tissues. In this paper we report the cloning of cDNAs encoding adenosine kinase from both rat and human tissues. Two distinct forms of adenosine kinase mRNA were identified in human tissues. Sequence variation between the two forms is restricted to the extreme 5'-end of the adenosine kinase mRNA, including a portion of the coding region, and is consistent with differential splicing of a single transcriptional product. We have expressed both forms in E. coli and produced soluble active enzyme which catalyzes the phosphorylation of adenosine with high specific activity in vitro and is susceptible to known adenosine kinase inhibitors.
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Affiliation(s)
- T McNally
- Division of Advanced Technology, Abbott Laboratories, Abbott Park, Illinois 60064-3500, USA
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Spychala J, Datta NS, Takabayashi K, Datta M, Fox IH, Gribbin T, Mitchell BS. Cloning of human adenosine kinase cDNA: sequence similarity to microbial ribokinases and fructokinases. Proc Natl Acad Sci U S A 1996; 93:1232-7. [PMID: 8577746 PMCID: PMC40062 DOI: 10.1073/pnas.93.3.1232] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Adenosine kinase catalyzes the phosphorylation of adenosine to AMP and hence is a potentially important regulator of extracellular adenosine concentrations. Despite extensive characterization of the kinetic properties of the enzyme, its primary structure has never been elucidated. Full-length cDNA clones encoding catalytically active adenosine kinase were obtained from lymphocyte, placental, and liver cDNA libraries. Corresponding mRNA species of 1.3 and 1.8 kb were noted on Northern blots of all tissues examined and were attributable to alternative polyadenylylation sites at the 3' end of the gene. The encoding protein consists of 345 amino acids with a calculated molecular size of 38.7 kDa and does not contain any sequence similarities to other well-characterized mammalian nucleoside kinases, setting it apart from this family of structurally and functionally related proteins. In contrast, two regions were identified with significant sequence identity to microbial ribokinase and fructokinases and a bacterial inosine/guanosine kinase. Thus, adenosine kinase is a structurally distinct mammalian nucleoside kinase that appears to be akin to sugar kinases of microbial origin.
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Affiliation(s)
- J Spychala
- Department of Pharmacology, University of North Carolina, Chapel Hill 27599, USA
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Mimouni M, Bontemps F, Van den Berghe G. Production of adenosine and nucleoside analogs by the exchange reaction catalyzed by rat liver adenosine kinase. Biochem Pharmacol 1995; 50:1587-91. [PMID: 7503760 DOI: 10.1016/0006-2952(95)02033-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
We have previously shown [8] that rat liver adenosine kinase can produce [14C]AMP from [14C]adenosine (Ado) and unlabelled adenosine monophosphate (AMP), in the absence of ATP, by an exchange reaction. In this study, we investigated whether Ado or AMP could be replaced in this exchange reaction by other nucleosides or nucleoside monophosphates (NMP), respectively. In the presence of 1 mM of the unlabelled NMP analogs 7-deazaadenosine (tubercidin) 5'-monophosphate, 6-chloropurine riboside 5'-monophosphate, or N6-methyl-AMP, [14C]AMP was formed from 20 microM [14C]Ado at up to 50% of the rate recorded with 1 mM unlabelled AMP. In the presence of 0.2 mM of the unlabelled analog nucleosides tubercidin, N6-methyladenosine, or 6-methylmercaptopurine riboside, [14C]Ado was generated from 1 mM [14C]AMP at up to 60% of the rate recorded with 0.2 mM unlabeled Ado. Small amounts of [14C]Ado were also formed from the natural nucleosides 5-amino-4-imidazolecarboxamide (AICA) riboside or 2'-deoxyadenosine. Administration of therapeutic anticancer and antiviral nucleosides that can serve as substrates for the exchange reaction catalyzed by adenosine kinase might, thus, result in a net production of Ado, a potent autacoid with physiological effects in numerous tissues.
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Affiliation(s)
- M Mimouni
- Laboratory of Physiological Chemistry, University of Louvain Medical School, Brussels, Belgium
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Abstract
The mammalian deoxyribonucleoside kinases are deoxycytidine kinase, thymidine kinase 1 and 2 and deoxyguanosine kinase. These enzymes phosphorylate deoxyribonucleosides and thereby provide an alternative to de novo synthesis of DNA precursors. Their activities are essential for the activation of several chemotherapeutically important nucleoside analogues. In recent years, these enzymes have been thoroughly characterised with regard to structure, substrate specificity and patterns of expression. In this review, these results are reviewed and furthermore, the physiologic metabolic role of the anabolic enzymes is discussed in relation to catabolic pathways. The significance of this information for the development of therapeutic protocols and choice of animal model systems is discussed. Finally, alternative pathways for nucleoside analogue phosphorylation are surveyed, such as the phosphotransfer capacity of 5'-nucleotidase.
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Affiliation(s)
- E S Arnér
- Medical Nobel Institute for Biochemistry, Department of Medical Biochemistry and Biophysics, Karolinska Institute, Sweden
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Elalaoui A, Divita G, Maury G, Imbach JL, Goody RS. Intrinsic tryptophan fluorescence of bovine liver adenosine kinase, characterization of ligand binding sites and conformational changes. EUROPEAN JOURNAL OF BIOCHEMISTRY 1994; 221:839-46. [PMID: 8174564 DOI: 10.1111/j.1432-1033.1994.tb18798.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Bovine liver adenosine kinase is a 45-kDa monomeric protein which exhibits a characteristic intrinsic tryptophan fluorescence with a maximal excitation at 284 nm and an emission peak centered at 335 nm. A total of three tryptophan residues/molecule has been estimated by using a fluorescence titration method. Low values of Stern-Volmer quenching constants in the presence of either acrylamide or iodide (4.2 M-1 or 1.5 M-1, respectively) indicated that the tryptophan residues are relatively buried in the native molecule. Tryptophan residues also showed a high heterogeneity, with a fractional accessible fluorescence value for iodide of 0.65. The enzyme fluorescence was very sensitive to substrate binding, which induced a marked fluorescence quenching, a lower tryptophan accessibility to acrylamide and iodide, and an increase in the tryptophan heterogeneity. ADP or ATP showed a monophasic saturation curve consistent with the existence of one binding site. In contrast, adenosine and AMP gave biphasic saturation curves, suggesting the existence of at least two binding sites, with a high and a low affinity. The presence of MgCl2 increased the affinity of ATP or ADP, whereas the binding of adenosine or AMP was not affected.
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Affiliation(s)
- A Elalaoui
- Université de Montpellier II Sciences et Techniques du Languedoc, URA 488 du CNRS, France
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Bethlenfalvay NC, Lima JE, Banks RE. 2'-Deoxyadenosine metabolism in human and opossum Didelphis virginiana erythrocytes in vitro. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. B, COMPARATIVE BIOCHEMISTRY 1993; 106:641-5. [PMID: 8281758 DOI: 10.1016/0305-0491(93)90142-r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
1. In erythrocytes of both species, deamination and phosphorylation of dADO was completely inhibited by 5 microM 2'deoxycoformycin and 10 microM 5-ITU respectively. 2. Under physiologic conditions, provided with nanomolar concentrations of dADO there was complete deamination of dADO in human red cells. In opossum erythrocytes deamination and phosphorylation of the deoxynucleoside were nearly; additionally, 1-2% of the substrate was metabolized to AXP. 3. With ADA inhibited in intact red cells, apparent Km and Vmax for dADO were 0.5 vs 0.1 mM and 0.8 vs 6.25 mumol/g hg/hr in human and opossum cells, respectively. 4. In opossum red cell lysates, GTP was superior to ATP and to dATP as a phosphate donor in the dADO kinase reaction.
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Affiliation(s)
- N C Bethlenfalvay
- Department of Primary Care, Fitzimons Army Medical Center, Aurora, CO 80045
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29
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Bhaumik D, Datta AK. Immunochemical and catalytic characteristics of adenosine kinase from Leishmania donovani. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)83749-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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30
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The Application of Affinity Chromatography for the Separation of “High Km” and “Low Km” 5′-Nucleotidase and other AMP Metabolizing Enzymes. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1989. [DOI: 10.1007/978-1-4684-5676-9_19] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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31
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Yamada Y, Natsumeda Y, Yamaji Y, Weber G. Two distinct target sites on IMP dehydrogenase in chemotherapy. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1989; 253B:57-63. [PMID: 2575352 DOI: 10.1007/978-1-4684-5676-9_10] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Y Yamada
- Laboratory for Experimental Oncology, Indiana University School of Medicine, Indianapolis 46223
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Snyder FF, Dyer C, Seegmiller JE, Goldblum RM, Mills GC, Schmalstieg FC. Substrate inhibition of adenosine phosphorylation in adenosine deaminase deficiency and adenosine-mediated inhibition of PP-ribose-P dependent nucleotide synthesis in hypoxanthine phosphoribosyltransferase deficient erythrocytes. J Inherit Metab Dis 1988; 11:174-83. [PMID: 2459496 DOI: 10.1007/bf01799869] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The metabolism of adenosine and its effects on phosphoribosylpyrophosphate, PP-ribose-P, dependent nucleotide synthesis were studied using erythrocytes from patients with adenosine deaminase and hypoxanthine phosphoribosyltransferase deficiency as models. The phosphorylation of adenosine was progressively inhibited by concentrations of adenosine greater than 1 mumol L-1 for control and ADA deficient erythrocytes. There was essentially no initial rate of phosphorylation at 30 mumol L-1 adenosine. Adenosine, 1 mumol L-1, also caused a 60% reduction in PP-ribose-P concentration in ADA deficient erythrocytes. For HPRT deficient erythrocytes in which ADA activity was blocked by coformycin, 10 mumol L-1 inosine stimulated PP-ribose-P dependent nucleotide synthesis from adenine, whereas, 10 mumol L-1 adenosine inhibited nucleotide synthesis. These observations suggest that adenosine phosphorylation and PP-ribose-P dependent nucleotide synthesis are inhibited under conditions in which adenosine accumulates, such as in hereditary or pharmacologically induced ADA deficiency.
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Affiliation(s)
- F F Snyder
- Department of Medical Biochemistry, University of Calgary, Alberta, Canada
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Ogasawara N, Goto H, Yamada Y, Nishigaki I, Itoh T, Hasegawa I, Park KS. Deficiency of AMP deaminase in erythrocytes. Hum Genet 1987; 75:15-8. [PMID: 3804327 DOI: 10.1007/bf00273831] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Six individuals with complete deficiency of erythrocyte AMP deaminase have been discovered. They are all healthy and have no hematological disorders. The deficiency is only in isozyme E, which is the erythrocyte type isozyme, and is inherited as an autosomal recessive trait. The frequency of the mutant gene is surprisingly high, one heterozygote in about 30 of the population in Japan, Seoul, and Taipei. The ATP level is approximately 50% higher in AMP-deficient erythrocytes compared to that of control cells. Degradation of adenine nucleotide is slower in the deficient erythrocytes than in the control erythrocytes.
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Hurley MC, Lin B, Fox IH. Regulation of deoxyadenosine and nucleoside analog phosphorylation by human placental adenosine kinase. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1986; 195 Pt B:141-9. [PMID: 3020902 DOI: 10.1007/978-1-4684-1248-2_22] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The enzymes responsible for phosphorylation of adenosine and nucleoside analogs are important in the pathogenesis of adenosine deaminase deficiency and for the activation of specific anticancer and antiviral drugs. We examined the role of adenosine kinase in catalyzing these reactions using an enzyme purified 4000-fold (2.1 umol/min/mg) from human placenta. The Km values of adenosine and ATP are 135 uM and 4 uM, respectively. Adenosine kinase phosphorylates adenine arabinoside with an apparent Km value of 1 mM using adenosine kinase assay conditions. The Km values for 6-methylmercaptopurine riboside and 5-iodotubercidin, substrates for adenosine kinase, are estimated to be 4.5 uM and 2.6 nM, respectively. These data indicate that dadenosine phosphorylation by adenosine kinase is primarily regulated by its Km, and the concentrations of Mg2+, ADP and AMP. The high Km values for phosphorylation of dadenosine and adenine arabinoside suggest that adenosine kinase may be less likely to phosphorylate these nucleosides in vivo than other enzymes with lower Km values. Adenosine kinase appears to be important for adenosine analog phosphorylation where the Michaelis constant is in the low micromolar range.
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Regulation of deoxyadenosine and nucleoside analog phosphorylation by human placental adenosine kinase. J Biol Chem 1985. [DOI: 10.1016/s0021-9258(17)36311-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Rotllan P, Miras Portugal MT. Adenosine kinase from bovine adrenal medulla. EUROPEAN JOURNAL OF BIOCHEMISTRY 1985; 151:365-71. [PMID: 2992963 DOI: 10.1111/j.1432-1033.1985.tb09110.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Adenosine kinase from bovine adrenal medulla was purified 1600-fold by using ammonium sulfate precipitation, gel filtration and affinity chromatography. Gel filtration yielded a relative molecular mass around 42000 and Michaelis constants were 0.2 microM for adenosine and 20 microM for MgATP. The enzyme showed a broad specificity for purine nucleoside triphosphate as phosphate donors. Both free Mg2+ and ATP were inhibitors. AMP was a competitive inhibitor with regard to adenosine and a non-competitive inhibitor versus MgATP, while ADP was a uncompetitive inhibitor with regard to adenosine and a non-competitive inhibitor versus MgATP. Adenosine kinase was strongly inhibited by the bis(adenylyl) polyphosphates Ap4A and Ap5A. These compounds inhibited the enzyme competitively versus MgATP (Ki = 0.06 microM for Ap4A and 0.4 microM for Ap5A) and uncompetitively with regard to adenosine. The results of the kinetic analysis suggest an ordered bi-bi mechanism, adenosine being the first substrate. The phosphorylation of adenosine was unaffected in the presence of vanadate ions.
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Abstract
The synthesis of purine nucleotides from the salvage precursors adenine and adenosine, and from the de novo precursors formate and glycine, was studied in isolated adrenal chromaffin cells. Both [8-14C]adenine and [8-14C]adenosine from extracellular medium are effectively incorporated into intracellular nucleotides. [14C]Formate and [U-14C]glycine are also incorporated, but de novo synthesis is clearly lower than synthesis from salvage precursors, although similar to de novo synthesis in liver. The enzymes responsible for adenine and adenosine salvage, adenine phosphoribosyltransferase and adenosine kinase, were purified about 1,500-fold. Both enzymes are mainly cytosolic and exhibit a similar molecular weight of around 42,000. The results suggest that chromaffin cells can replenish their intracellular nucleotides lost during the secretory event by an active synthesis from salvage and de novo precursors.
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Tryon VV, Pollack D. Purine metabolism in Acholeplasma laidlawii B: novel PPi-dependent nucleoside kinase activity. J Bacteriol 1984; 159:265-70. [PMID: 6330034 PMCID: PMC215623 DOI: 10.1128/jb.159.1.265-270.1984] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Acholeplasma laidlawii B-PG9 was examined for 16 cytoplasmic enzymes with activity for purine salvage and interconversion. Phosphoribosyltransferase activities for adenine, guanine, xanthine, and hypoxanthine were shown. Adenine, guanine, xanthine, and hypoxanthine were ribosylated to their nucleoside. Adenosine, inosine, xanthosine, and guanosine were converted to their base. No ATP-dependent phosphorylation of nucleosides to mononucleotides was found. However, PPi-dependent phosphorylation of adenosine, inosine, and guanosine to AMP, inosine monophosphate, and GMP, respectively, was detected. Nucleotidase activity for AMP, inosine monophosphate, xanthosine monophosphate, and GMP was also found. Interconversion of GMP to AMP was detected. Enzyme activities for the interconversion of AMP to GMP were not detected. Therefore, A. laidlawii B-PG9 cannot synthesize guanylates from adenylates or inosinates. De novo synthesis of purines was not detected. This study demonstrates that A. laidlawii B-PG9 has the enzyme activities for the salvage and limited interconversion of purines and, except for purine nucleoside kinase activity, is similar to Mycoplasma mycoides subsp. mycoides. This is the first report of a PPi-dependent nucleoside kinase activity in any organism.
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Yamada Y, Goto H, Ogasawara N. Purine nucleoside kinases in human T- and B-lymphoblasts. BIOCHIMICA ET BIOPHYSICA ACTA 1983; 761:34-40. [PMID: 6315069 DOI: 10.1016/0304-4165(83)90359-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Purine nucleoside kinases in human B- and T-lymphoblasts were fractionated by DEAE-cellulose chromatography. Human B-lymphoblast cell extracts showed three peaks of nucleoside kinase activities, adenosine kinase (EC 2.7.1.20), deoxyguanosine kinase and deoxycytidine kinase (EC 2.7.1.74). However, T-lymphoblast cell extracts showed a nucleoside kinase activity which phosphorylates deoxycytidine, deoxyadenosine and deoxyguanosine, similar to deoxycytidine kinase, in addition to the three nucleoside kinases. The Km values of T-lymphoblast-specific nucleoside kinase for deoxyadenosine and deoxyguanosine, 15 and 26 microM, respectively, were smaller than those of deoxycytidine kinase, 150 and 330 microM, respectively. Deoxyadenosine phosphorylation by deoxycytidine kinase was strongly inhibited by dCTP, but the phosphorylation by T-lymphoblast-specific nucleoside kinase was only weakly inhibited by dCTP. Deoxyadenosine phosphorylating activity in B-lymphoblast extracts was more distinctly inhibited by dCTP than that in T-lymphoblast extracts.
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Hurley MC, Fox IH. Measurement of nucleoside kinases in crude tissue extracts. BIOCHEMICAL MEDICINE 1983; 30:89-100. [PMID: 6312976 DOI: 10.1016/0006-2944(83)90011-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The measurements of deoxyadenosine kinase, adenosine kinase, and deoxycytidine kinase were examined in human placental cytosol to achieve a valid and reliable assay linear with time and protein. Our studies confirm the need to inhibit deaminase enzymes, since deoxyadenosine and deoxycytidine undergo extensive deamination and phosphorolysis. The use of a uniformly labeled nucleoside substrate introduced an artifact because the chromatographic behavior of the deoxyribose-1-phosphate, formed during the assay, was difficult to distinguish from the deoxynucleoside phosphate product. Accurate product identification was also essential. Finally, the substitution of GTP in place of ATP as the phosphate donor, the addition of a sulfhydryl reducing agent and a monovalent cation need to be considered when an assay is optimized. The use of these methods have lead to valid assays in placental cytosol that are linear with time and protein. Consideration of these important principles are necessary when establishing a valid and reliable nucleoside kinase assay in a crude tissue preparation.
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Yamada Y, Goto H, Ogasawara N. Deoxyguanosine kinase from human placenta. BIOCHIMICA ET BIOPHYSICA ACTA 1982; 709:265-72. [PMID: 6295492 DOI: 10.1016/0167-4838(82)90469-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Deoxyguanosine kinase (ATP:deoxyguanosine 5'-phosphotransferase) has been purified up to a specific activity of 10.3 nmol/min per mg protein from human placenta. The enzyme appears to have a molecular weight of 58 000 from the results of Sephadex G-75 gel filtration. The enzyme catalyzed phosphorylation of deoxyguanosine and deoxyadenosine, but deoxycytidine was not phosphorylated. An apparent Km value for deoxyguanosine was 2.5 micro M. When ATP was used as a phosphate donor, the pH optimum was at pH 6.0, but the optimum was shifted to pH 6.8 by the addition of dTTP. At physiological pH, the activity was stimulated 3-4-fold by dTTP. dTTP was also an effective phosphate donor, but using dTTP as a phosphate donor, a broad pH optimum of 7.0 was observed. Two Km values of 0.13 and 2.2 mM were obtained for both MgATP2- and MgdTTP2-. The activity was strongly inhibited by dGTP and dGDP; 50% inhibition by 1.0 micro M dGTP and 2.1 micro M dGDP, respectively. The enzyme required the presence o Mg2+ or Mn2+.
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Yamada Y, Goto H, Ogasawara N. Differences of adenosine kinases from various mammalian tissues. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. B, COMPARATIVE BIOCHEMISTRY 1982; 71:367-72. [PMID: 6279355 DOI: 10.1016/0305-0491(82)90396-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
1. Adenosine kinases purified to homogeneity from various mammalian tissues have a monomeric structure, and their molecular weights were estimated around 40,000. 2. The enzyme activity per wet weight of tissue appears to vary from source to source, but the specific activities of the final enzyme preparations were alike, which were 6.3--7.8 mumol/min/mg protein. 3. No or small difference was observed in the kinetic properties among all seven adenosine kinases. 4. Some differences in structure were observed among five liver enzymes from human, rabbit, rat, mouse and Mongolian gerbil, but no difference was observed between the enzymes from human placenta and liver, or the enzymes from rat liver and brain.
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