title: A Solanum tuberosum inositol phosphate kinase (StITPK1) displaying inositol phosphate-inositol phosphate and inositol phosphate-ADP phosphotransferase activities.
abstract: We describe a multifunctional inositol polyphosphate kinase/phosphotransferase from Solanum tuberosum, StITPKalpha (GenBank accession number: EF362784), hereafter called StITPK1. StITPK1 displays inositol 3,4,5,6-tetrakisphosphate 1-kinase activity: K(m) = 27 microM, and V(max) = 19 nmol min(-1) mg(-1). The enzyme displays inositol 1,3,4,5,6-pentakisphosphate 1-phosphatase activity in the absence of a nucleotide acceptor and inositol 1,3,4,5,6-pentakisphosphate-ADP phosphotransferase activity in the presence of physiological concentrations of ADP. Additionally, StITPK1 shows inositol phosphate-inositol phosphate phosphotransferase activity. Homology modelling provides a structural rationale of the catalytic abilities of StITPK1. Inter-substrate transfer of phosphate groups between inositol phosphates is an evolutionarily conserved function of enzymes of this class.
authors.affiliation: School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK.
authors.forename: Samuel E K
authors.initials: SE
authors.lastname: Caddick
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Harrison
authors.forename: Ioanna
authors.initials: I
authors.lastname: Stavridou
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Mitchell
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Hemmings
authors.forename: Charles A
authors.initials: CA
authors.lastname: Brearley
mesh_terms: D000244:Adenosine Diphosphate / Q000737:chemistry*; D000595:Amino Acid Sequence; D002384:Catalysis; D003001:Cloning, Molecular; D007295:Inositol Phosphates / Q000737:chemistry*; D008969:Molecular Sequence Data; D010744:Phosphoric Monoester Hydrolases / Q000737:chemistry; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000737:chemistry* / Q000235:genetics; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics; D017433:Protein Structure, Secondary; D011198:Solanum tuberosum / Q000201:enzymology*; D013379:Substrate Specificity
chemical_list: D007295:Inositol Phosphates; D010940:Plant Proteins; C013571:inositol pentaphosphate; D000244:Adenosine Diphosphate; D017853:Phosphotransferases (Alcohol Group Acceptor); C072095:inositol 1,3,4,5,6-pentakisphosphate-1-3-phosphatase; D010744:Phosphoric Monoester Hydrolases