A novel mammalian glucokinase exhibiting exclusive inorganic polyphosphate dependence in the cell nucleus
Background: Hexokinase and glucokinase enzymes are ubiquitously expressed and use ATP and ADP as substrates in mammalian systems and a variety of polyphosphate substrates and/or ATP in some eukaryotic and microbial systems. Polyphosphate synthesising or utilizing enzymes are widely expressed in micr...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Elsevier
2017-12-01
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| Series: | Biochemistry and Biophysics Reports |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S2405580817301929 |
| _version_ | 1818499611524857856 |
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| author | Antasar Ali D. Claire Wathes Angelina Swali Helena Burns Shamus Burns |
| author_facet | Antasar Ali D. Claire Wathes Angelina Swali Helena Burns Shamus Burns |
| author_sort | Antasar Ali |
| collection | DOAJ |
| description | Background: Hexokinase and glucokinase enzymes are ubiquitously expressed and use ATP and ADP as substrates in mammalian systems and a variety of polyphosphate substrates and/or ATP in some eukaryotic and microbial systems. Polyphosphate synthesising or utilizing enzymes are widely expressed in microbial systems but have not been reported in mammalian systems, despite the presence of polyphosphate in mammalian cells. Only two micro-organisms have previously been shown to express an enzyme that uses polyphosphate exclusively.
Methods: A variety of experimental approaches, including NMR and NAD-linked assay systems were used to conduct a biochemical investigation of polyphosphate dependent glucokinase activity in mammalian tissues.
Results: A novel mammalian glucokinase, highly responsive to hexametaphosphate (HMP) but not ATP or ADP as a phosphoryl donor is present in the nuclei of mammalian hepatocytes. The liver enzyme exhibited sigmoidal kinetics with respect to glucose with a S0.5 of 12 mM, similar to the known kinetics of mammalian ATP-glucokinase. The Km for HMP (0.5 mM) was also similar to that of phosphoryl donors for mammalian ATP-glucokinases. The new enzyme was inhibited by several nucleotide phosphates.
Conclusions: We report the discovery of a polyphosphate-dependent enzyme system in mammalian cells with kinetics similar to established ATP-dependent glucokinase, also known to have a nuclear location. The kinetics suggest possible regulatory or redox protective roles.
General significance: The role of polyphosphate in mammalian systems has remained an enigma for decades, and the present report describes progress on the significance of this compound in intracellular metabolism in mammals. |
| first_indexed | 2024-12-10T20:31:51Z |
| format | Article |
| id | doaj.art-a45ef7bef1504c6b9614dff7bfe8c1a6 |
| institution | Directory Open Access Journal |
| issn | 2405-5808 |
| language | English |
| last_indexed | 2024-12-10T20:31:51Z |
| publishDate | 2017-12-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Biochemistry and Biophysics Reports |
| spelling | doaj.art-a45ef7bef1504c6b9614dff7bfe8c1a62022-12-22T01:34:40ZengElsevierBiochemistry and Biophysics Reports2405-58082017-12-0112C15115710.1016/j.bbrep.2017.09.004A novel mammalian glucokinase exhibiting exclusive inorganic polyphosphate dependence in the cell nucleusAntasar Ali0D. Claire Wathes1Angelina Swali2Helena Burns3Shamus Burns4Biological Sciences, University of Huddersfield, Huddersfield UK HD1 3DH, United KingdomDepartment of Pathobiology and Population Sciences, The Royal Veterinary College, London UK NW1 0TU, United KingdomSchool of Biosciences, University of Nottingham, Nottingham UK LE12 5RD, United KingdomBiological Sciences, University of Huddersfield, Huddersfield UK HD1 3DH, United KingdomBiological Sciences, University of Huddersfield, Huddersfield UK HD1 3DH, United KingdomBackground: Hexokinase and glucokinase enzymes are ubiquitously expressed and use ATP and ADP as substrates in mammalian systems and a variety of polyphosphate substrates and/or ATP in some eukaryotic and microbial systems. Polyphosphate synthesising or utilizing enzymes are widely expressed in microbial systems but have not been reported in mammalian systems, despite the presence of polyphosphate in mammalian cells. Only two micro-organisms have previously been shown to express an enzyme that uses polyphosphate exclusively. Methods: A variety of experimental approaches, including NMR and NAD-linked assay systems were used to conduct a biochemical investigation of polyphosphate dependent glucokinase activity in mammalian tissues. Results: A novel mammalian glucokinase, highly responsive to hexametaphosphate (HMP) but not ATP or ADP as a phosphoryl donor is present in the nuclei of mammalian hepatocytes. The liver enzyme exhibited sigmoidal kinetics with respect to glucose with a S0.5 of 12 mM, similar to the known kinetics of mammalian ATP-glucokinase. The Km for HMP (0.5 mM) was also similar to that of phosphoryl donors for mammalian ATP-glucokinases. The new enzyme was inhibited by several nucleotide phosphates. Conclusions: We report the discovery of a polyphosphate-dependent enzyme system in mammalian cells with kinetics similar to established ATP-dependent glucokinase, also known to have a nuclear location. The kinetics suggest possible regulatory or redox protective roles. General significance: The role of polyphosphate in mammalian systems has remained an enigma for decades, and the present report describes progress on the significance of this compound in intracellular metabolism in mammals.http://www.sciencedirect.com/science/article/pii/S2405580817301929GlucokinaseHexokinasePolyphosphateEvolution |
| spellingShingle | Antasar Ali D. Claire Wathes Angelina Swali Helena Burns Shamus Burns A novel mammalian glucokinase exhibiting exclusive inorganic polyphosphate dependence in the cell nucleus Biochemistry and Biophysics Reports Glucokinase Hexokinase Polyphosphate Evolution |
| title | A novel mammalian glucokinase exhibiting exclusive inorganic polyphosphate dependence in the cell nucleus |
| title_full | A novel mammalian glucokinase exhibiting exclusive inorganic polyphosphate dependence in the cell nucleus |
| title_fullStr | A novel mammalian glucokinase exhibiting exclusive inorganic polyphosphate dependence in the cell nucleus |
| title_full_unstemmed | A novel mammalian glucokinase exhibiting exclusive inorganic polyphosphate dependence in the cell nucleus |
| title_short | A novel mammalian glucokinase exhibiting exclusive inorganic polyphosphate dependence in the cell nucleus |
| title_sort | novel mammalian glucokinase exhibiting exclusive inorganic polyphosphate dependence in the cell nucleus |
| topic | Glucokinase Hexokinase Polyphosphate Evolution |
| url | http://www.sciencedirect.com/science/article/pii/S2405580817301929 |
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