A Solanum tuberosum inositol phosphate kinase (StITPK1) displaying inositol phosphate-inositol phosphate and inositol phosphate-ADP phosphotransferase activities |
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Authors: | Caddick Samuel E K Harrison Christopher J Stavridou Ioanna Mitchell Jennifer L Hemmings Andrew M Brearley Charles A |
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Institution: | School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK. |
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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. |
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Keywords: | AMPPCP 5′-adenosyl-methylene-triphosphate |
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