title: Biochemical characterization of human gluconokinase and the proposed metabolic impact of gluconic acid as determined by constraint based metabolic network analysis.
abstract: The metabolism of gluconate is well characterized in prokaryotes where it is known to be degraded following phosphorylation by gluconokinase. Less is known of gluconate metabolism in humans. Human gluconokinase activity was recently identified proposing questions about the metabolic role of gluconate in humans. Here we report the recombinant expression, purification and biochemical characterization of isoform I of human gluconokinase alongside substrate specificity and kinetic assays of the enzyme catalyzed reaction. The enzyme, shown to be a dimer, had ATP dependent phosphorylation activity and strict specificity towards gluconate out of 122 substrates tested. In order to evaluate the metabolic impact of gluconate in humans we modeled gluconate metabolism using steady state metabolic network analysis. The results indicate that significant metabolic flux changes in anabolic pathways linked to the hexose monophosphate shunt (HMS) are induced through a small increase in gluconate concentration. We argue that the enzyme takes part in a context specific carbon flux route into the HMS that, in humans, remains incompletely explored. Apart from the biochemical description of human gluconokinase, the results highlight that little is known of the mechanism of gluconate metabolism in humans despite its widespread use in medicine and consumer products.
authors.affiliation: Center for Systems Biology, University of Iceland, Reykjavik, Iceland; University of Iceland Biomedical Center, Reykjavik, Iceland.
authors.forename: Neha
authors.initials: N
authors.lastname: Rohatgi
authors.affiliation: Center for Protein Research, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Tine Kragh
authors.initials: TK
authors.lastname: Nielsen
authors.affiliation: Center for Protein Research, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Sara Petersen
authors.initials: SP
authors.lastname: Bjørn
authors.affiliation: Center for Systems Biology, University of Iceland, Reykjavik, Iceland.
authors.forename: Ivar
authors.initials: I
authors.lastname: Axelsson
authors.affiliation: Center for Systems Biology, University of Iceland, Reykjavik, Iceland.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Paglia
authors.affiliation: Center for Protein Research, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Bjørn Gunnar
authors.initials: BG
authors.lastname: Voldborg
authors.affiliation: Center for Systems Biology, University of Iceland, Reykjavik, Iceland.
authors.forename: Bernhard O
authors.initials: BO
authors.lastname: Palsson
authors.affiliation: Center for Systems Biology, University of Iceland, Reykjavik, Iceland; University of Iceland Biomedical Center, Reykjavik, Iceland.
authors.forename: Óttar
authors.initials: Ó
authors.lastname: Rolfsson
mesh_terms: D004912:Erythrocytes / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology; D005942:Gluconates / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D053858:Metabolic Networks and Pathways; D008958:Models, Molecular; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000737:chemistry* / Q000378:metabolism*; D011487:Protein Conformation; D013379:Substrate Specificity
chemical_list: D005942:Gluconates; D017853:Phosphotransferases (Alcohol Group Acceptor); C020578:gluconokinase; C030691:gluconic acid