title: Metabolic and signaling properties of an Itpk gene family in Glycine max.
abstract: We have cloned and characterized four Itpk genes from soybean. All four recombinant Itpk proteins showed canonical Ins(1,3,4)P3 5/6-kinase activity, but a kinetic analysis raised questions about its biological significance. Instead, we provide evidence that one alternative biological role for soybean Itpks is to interconvert the Cl(-) channel inhibitor, Ins(3,4,5,6)P4, and its metabolic precursor, Ins(1,3,4,5,6)P5, within a substrate cycle. The soybean Itpks also phosphorylated Ins(3,4,6)P3 to Ins(1,3,4,6)P4 which was further phosphorylated to Ins(1,3,4,5,6)P5 by soybean Ipk2. Thus, soybean Itpks may participate in an inositol lipid-independent pathway of InsP6 synthesis.
authors.affiliation: Department of Plant Pathology, Physiology and Weed Science, Virginia Polytechnic Institute and State University, 413 Price Hall, Blacksburg, VA 24061, USA.
authors.forename: Amanda R
authors.initials: AR
authors.lastname: Stiles
authors.forename: Xun
authors.initials: X
authors.lastname: Qian
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Shears
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Grabau
mesh_terms: D000595:Amino Acid Sequence; D017343:Genes, Plant; D007295:Inositol Phosphates / Q000378:metabolism; D008969:Molecular Sequence Data; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism*; D010833:Phytic Acid / Q000096:biosynthesis*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D013025:Glycine max / Q000201:enzymology* / Q000235:genetics
chemical_list: D007295:Inositol Phosphates; D010940:Plant Proteins; D011994:Recombinant Proteins; C118500:inositol 3,4,5-trisphosphate; C451920:inositol-1,3,4,5,6-pentakisphosphate; C081652:inositol-3,4,5,6-tetrakisphosphate; D010833:Phytic Acid; D017853:Phosphotransferases (Alcohol Group Acceptor); C056875:myo-inositol-trisphosphate 6-kinase