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myo-inositol pentakisphosphates. Structure, biological occurrence and phosphorylation to myo-inositol hexakisphosphate. 1991

L R Stephens, and P T Hawkins, and A F Stanley, and T Moore, and D R Poyner, and P J Morris, and M R Hanley, and R R Kay, and R F Irvine
Biochemistry Department, AFRC, Babraham, Cambridge, U.K.

1. Standard and high-performance anion-exchange-chromatographic techniques have been used to purify myo-[3H]inositol pentakisphosphates from various myo-[3H]inositol-prelabelled cells. Slime mould (Dictyostelium discoideum) contained 8 microM-myo-[3H]inositol 1,3,4,5,6-pentakisphosphate, 16 microM-myo-[3H]inositol 1,2,3,4,6-pentakisphosphate and 36 microM-D-myo-[3H]inositol 1,2,4,5,6-pentakisphosphate [calculated intracellular concentrations; Stephens & Irvine (1990) Nature (London) 346, 580-583]; germinating mung-bean (Phaseolus aureus) seedlings contained both D- and L-myo-[3H]inositol 1,2,4,5,6-pentakisphosphate (which was characterized by 31P and two-dimensional proton n.m.r.) and D- and/or L-myo-[3H]inositol 1,2,3,4,5-pentakisphosphate; HL60 cells contained myo-[3H]inositol 1,3,4,5,6-pentakisphosphate (in a 500-fold excess over the other species), myo-[3H]inositol 1,2,3,4,6-pentakisphosphate and D- and/or L-myo-[3H]inositol 1,2,4,5,6-pentakisphosphate; and NG-115-401L-C3 cells contained myo-[3H]inositol 1,3,4,5,6-pentakisphosphate (in a 100-fold excess over the other species), D- and/or L-myo-[3H]inositol 1,2,4,5,6-pentakisphosphate, myo-[3H]inositol 1,2,3,4,6-pentakisphosphate and D- and/or L-myo-[3H]inositol 1,2,3,4,5-pentakisphosphate. 2. Multiple soluble ATP-dependent myo-inositol pentakisphosphate kinase activities have been detected in slime mould, rat brain and germinating mung-bean seedling homogenates. In slime-mould cytosolic fractions, the three myo-inositol pentakisphosphates that were present in intact slime moulds could be phosphorylated to myo-[3H]inositol hexakisphosphate: the relative first-order rate constants for these reactions were, in the order listed above, 1:8:31 respectively (with first-order rate constants in the intact cell of 0.1, 0.8 and 3.1 s-1, assuming a cytosolic protein concentration of 50 mg/ml), and the Km values of the activities for their respective inositol phosphate substrates (in the presence of 5 mM-ATP) were 1.6 microM, 3.8 microM and 1.4 microM. At least two forms of myo-inositol pentakisphosphate kinase activity could be resolved from a slime-mould cytosolic fraction by both pharmacological and chromatographic criteria. Rat brain cytosol and a soluble fraction derived from germinating mung-bean seedlings could phosphorylate myo-inositol D/L-1,2,4,5,6-, D/L-1,2,3,4,5-, 1,2,3,4,6- and 1,3,4,5,6-pentakisphosphates to myo-inositol hexakisphosphate: the relative first-order rate constants were 57:27:77:1 respectively for brain cytosol (with first-order rate constants in the intact cell of 0.0041, 0.0019, 0.0056 and 0.000073 s-1 respectively, assuming a cytosolic protein concentration of 50 mg/ml) and 1:11:12:33 respectively for mung-bean cytosol (with first-order rate constants in a supernatant fraction with a protein concentration of 10 mg/ml of 0.0002, 0.0022, 0.0024 and 0.0066 s-1 respectively).

UI MeSH Term Description Entries
D007295 Inositol Phosphates Phosphoric acid esters of inositol. They include mono- and polyphosphoric acid esters, with the exception of inositol hexaphosphate which is PHYTIC ACID. Inositol Phosphate,Phosphate, Inositol,Phosphates, Inositol
D007536 Isomerism The phenomenon whereby certain chemical compounds have structures that are different although the compounds possess the same elemental composition. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed) Isomerisms
D007700 Kinetics The rate dynamics in chemical or physical systems.
D009682 Magnetic Resonance Spectroscopy Spectroscopic method of measuring the magnetic moment of elementary particles such as atomic nuclei, protons or electrons. It is employed in clinical applications such as NMR Tomography (MAGNETIC RESONANCE IMAGING). In Vivo NMR Spectroscopy,MR Spectroscopy,Magnetic Resonance,NMR Spectroscopy,NMR Spectroscopy, In Vivo,Nuclear Magnetic Resonance,Spectroscopy, Magnetic Resonance,Spectroscopy, NMR,Spectroscopy, Nuclear Magnetic Resonance,Magnetic Resonance Spectroscopies,Magnetic Resonance, Nuclear,NMR Spectroscopies,Resonance Spectroscopy, Magnetic,Resonance, Magnetic,Resonance, Nuclear Magnetic,Spectroscopies, NMR,Spectroscopy, MR
D010761 Phosphorus Radioisotopes Unstable isotopes of phosphorus that decay or disintegrate emitting radiation. P atoms with atomic weights 28-34 except 31 are radioactive phosphorus isotopes. Radioisotopes, Phosphorus
D010766 Phosphorylation The introduction of a phosphoryl group into a compound through the formation of an ester bond between the compound and a phosphorus moiety. Phosphorylations
D010770 Phosphotransferases A rather large group of enzymes comprising not only those transferring phosphate but also diphosphate, nucleotidyl residues, and others. These have also been subdivided according to the acceptor group. (From Enzyme Nomenclature, 1992) EC 2.7. Kinases,Phosphotransferase,Phosphotransferases, ATP,Transphosphorylase,Transphosphorylases,Kinase,ATP Phosphotransferases
D010833 Phytic Acid Complexing agent for removal of traces of heavy metal ions. It acts also as a hypocalcemic agent. Inositol Hexaphosphate,Phytin,Calcium Phytate,Inositol Hexakisphosphate,Phytate,Sodium Phytate,Acid, Phytic,Hexakisphosphate, Inositol,Hexaphosphate, Inositol,Phytate, Calcium,Phytate, Sodium
D010944 Plants Multicellular, eukaryotic life forms of kingdom Plantae. Plants acquired chloroplasts by direct endosymbiosis of CYANOBACTERIA. They are characterized by a mainly photosynthetic mode of nutrition; essentially unlimited growth at localized regions of cell divisions (MERISTEMS); cellulose within cells providing rigidity; the absence of organs of locomotion; absence of nervous and sensory systems; and an alternation of haploid and diploid generations. It is a non-taxonomical term most often referring to LAND PLANTS. In broad sense it includes RHODOPHYTA and GLAUCOPHYTA along with VIRIDIPLANTAE. Plant
D001921 Brain The part of CENTRAL NERVOUS SYSTEM that is contained within the skull (CRANIUM). Arising from the NEURAL TUBE, the embryonic brain is comprised of three major parts including PROSENCEPHALON (the forebrain); MESENCEPHALON (the midbrain); and RHOMBENCEPHALON (the hindbrain). The developed brain consists of CEREBRUM; CEREBELLUM; and other structures in the BRAIN STEM. Encephalon

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