ITPK1 (Inositol Tetrakisphosphate 1-Kinase)

Inositol polyphosphatases (IPPases) play an important role in the metabolism of inositol polyphosphates, a class of molecules involved in signal transduction. Here we characterize 2 new protein tyrosine phosphatase-like IPPases (PhyAsl and PhyBsl) cloned from Selenomonas lacticifex that can hydrolyze myo-inositol hexakisphosphate (InsP6) in vitro. To determine their preferred substrates and stereospecificity of InsP6 dephosphorylation, a combination of kinetic and high-performance ion pair chromatography studies were conducted. Despite only 33% amino acid sequence identity between them, both enzymes display strict specificity for IPP substrates and cleave InsP6 primarily at the d-3-phosphate position (>90%). Furthermore, both enzymes predominantly degrade InsP6 to Ins(2)P via identical and very specific routes of dephosphorylation (3,4,5,6,1). Despite these similarities, PhylAsl is shown to have a slight kinetic preference for the major inositol pentakisphosphate intermediate in its InsP6 hydrolysis pathway, whereas PhyBsl displays a unique and substantial preference for an inositol tetrakisphosphate intermediate.

Download Full-text

Rapid formation of inositol 1,3,4,5-tetrakisphosphate and inositol 1,3,4-trisphosphate in rat parotid glands may both result indirectly from receptor-stimulated release of inositol 1,4,5-trisphosphate from phosphatidylinositol 4,5-bisphosphate

Biochemical Journal ◽

10.1042/bj2380507 ◽

1986 ◽

Vol 238 (2) ◽

pp. 507-516 ◽

Cited By ~ 147

Author(s):

P T Hawkins ◽

L Stephens ◽

C P Downes

Keyword(s):

Initial Rate ◽

Parotid Glands ◽

Inositol 1,4,5 Trisphosphate ◽

Rapid Formation ◽

Inositol Tetrakisphosphate ◽

Rat Parotid ◽

Phosphatidylinositol 4 ◽

Hydrolysis Of ◽

Direct Hydrolysis ◽

Stimulation Of

Addition of 1 mM-carbachol to [3H]inositol-labelled rat parotid slices stimulated rapid formation of [3H]inositol 1,3,4,5-tetrakisphosphate, the accumulation of which reached a peak 20 s after stimulation, and then declined rapidly towards a new steady state. The initial rate of formation of inositol 1,3,4,5-tetrakisphosphate was slower than that for inositol 1,4,5-trisphosphate. The radioactivity in [3H]inositol 1,3,4,5-tetrakisphosphate fell quickly in carbachol-stimulated and then atropine-blocked parotid slices, suggesting that it is rapidly metabolized during stimulation. Parotid homogenates rapidly dephosphorylated inositol 1,4,5-trisphosphate, inositol 1,3,4,5-tetrakisphosphate and, less rapidly, inositol 1,3,4-trisphosphate. Inositol 1,3,4,5-tetrakisphosphate was specifically hydrolysed to a compound with the chromatographic properties of inositol 1,3,4-trisphosphate. The only 3H-labelled phospholipids that we could detect in parotid slices labelled with [3H]inositol for 90 min were phosphatidylinositol, phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate. Parotid homogenates synthesized inositol tetrakisphosphate from inositol 1,4,5-trisphosphate. This activity was dependent on the presence of ATP. We suggest that, during carbachol stimulation of parotid slices, the key event in inositol lipid metabolism is the activation of phosphatidylinositol 4,5-bisphosphate-specific phospholipase C. The inositol 1,4,5-trisphosphate thus liberated is metabolized in two distinct ways; by direct hydrolysis of the 5-phosphate to form inositol 1,4-bisphosphate and by phosphorylation to form inositol 1,3,4,5-tetrakisphosphate and hence, by hydrolysis of this tetrakisphosphate, to form inositol 1,3,4-trisphosphate.

Download Full-text

An inositol tetrakisphosphate-containing phospholipid in activated neutrophils

Nature ◽

10.1038/334353a0 ◽

1988 ◽

Vol 334 (6180) ◽

pp. 353-356 ◽

Cited By ~ 206

Author(s):

Alexis E. Traynor-Kaplan ◽

Anna L. Harris ◽

Barbara L. Thompson ◽

Palmer Taylor ◽

Larry A. Sklar

Keyword(s):

Activated Neutrophils ◽

Inositol Tetrakisphosphate

Download Full-text

l-myo-inositol 1,4,5,6-tetrakisphosphate is present in both mammalian and avian cells

Biochemical Journal ◽

10.1042/bj2490271 ◽

1988 ◽

Vol 249 (1) ◽

pp. 271-282 ◽

Cited By ~ 66

Author(s):

L Stephens ◽

P T Hawkins ◽

N Carter ◽

S B Chahwala ◽

A J Morris ◽

...

Keyword(s):

High Performance ◽

Periodic Acid ◽

Platelet Activating Factor ◽

Anion Exchange Chromatography ◽

Total Radioactivity ◽

Exchange Chromatography ◽

Murine Bone Marrow ◽

Cell Extracts ◽

Inositol 1,4,5 Trisphosphate ◽

Inositol Tetrakisphosphate

When myo-[3H]inositol-prelabelled primary-cultured murine bone-marrow-derived macrophages were challenged with platelet-activating factor (PAF; 200 ng/ml), there was a rapid (2.5-fold at 10 s) rise in the intracellular concentration of D-myo-[3H]inositol 1,4,5-trisphosphate, followed by a rise in myo-[3H]inositol tetrakisphosphate. myo-[3H]Inositol tetrakisphosphate fractions were isolated by high-performance anion-exchange chromatography from myo-[3H]inositol-prelabelled chick erythrocytes and primary-cultured macrophages. In both cases [3H]iditol and [3H]inositol were the only significant products (greater than 90% of recovered radioactivity) after oxidation to completion with periodic acid, reduction with NaBH4 and dephosphorylation with alkaline phosphatase. The presence of [3H]inositol after this procedure is consistent with the occurrence of [3H]inositol 1,3,4,5-tetrakisphosphate in the cell extracts, whereas [3H]iditol could only be derived from D- or L-inositol 1,4,5,6-tetrakisphosphate. When [3H]inositol tetrakisphosphate fractions obtained from (A) unstimulated macrophages, (B) macrophages that had been stimulated with PAF for 40s or (C) chick erythrocytes were subjected to the above procedure, radioactivity was recovered in these polyols in the following proportions: A, 60-90% in iditol, with 10-40% in inositol; B, total radioactivity increased by a factor of 9.8, 94% being recovered in inositol and 8% in iditol; C, 70-80% in iditol and 20-30% in inositol. [3H]Iditol derived from myo-[3H]inositol tetrakisphosphate fractions from macrophages and chick erythrocytes was oxidized to sorbose by L-iditol dehydrogenase (L-iditol:NAD+2-oxidoreductase, 1.1.1.14) at the same rate as authentic L-iditol. D-[14C]Iditol, derived from D-myo-inositol 1,4,5-trisphosphate, was not oxidized by L-iditol dehydrogenase. This result indicates that the [3H]iditol was derived from L-myo-inositol inositol 1,4,5,6-tetrakisphosphate. The data are consistent with rapid PAF-sensitive synthesis of D-myo-[3H]inositol 1,3,4,5-tetrakisphosphate in macrophages, and demonstrate that L-myo-inositol 1,4,5,6-tetrakisphosphate is synthesized in both mammalian and avian cells. The levels of L-myo-[3H]inositol 1,4,5,6-tetrakisphosphate in primary-cultured macrophages are not acutely sensitive to PAF.

Download Full-text

Studies on Avian Erythrocyte Metabolism. Inositol Tetrakisphosphate: the Major Phosphate Compound in the Erythrocytes of the Ostrich (Struthio camelus camelus)

European Journal of Biochemistry ◽

10.1111/j.1432-1033.1977.tb11700.x ◽

1977 ◽

Vol 77 (3) ◽

pp. 567-574 ◽

Cited By ~ 30

Author(s):

Russell ISAACKS ◽

Donald HARKNESS ◽

Janet ADLER ◽

Sandra ROTH ◽

Chang KIM ◽

...

Keyword(s):

Struthio Camelus ◽

Phosphate Compound ◽

Inositol Tetrakisphosphate ◽

Avian Erythrocyte ◽

Erythrocyte Metabolism

Download Full-text

Lithium inhibits muscarinic-receptor-stimulated inositol tetrakisphosphate accumulation in rat cerebral cortex

Biochemical Journal ◽

10.1042/bj2470797 ◽

1987 ◽

Vol 247 (3) ◽

pp. 797-800 ◽

Cited By ~ 59

Author(s):

I Batty ◽

S R Nahorski

Keyword(s):

Cerebral Cortex ◽

Steady State ◽

Inhibitory Action ◽

Rat Cerebral Cortex ◽

Phosphoinositide Metabolism ◽

Muscarinic Agonist ◽

Complex Action ◽

Inositol 1,4,5 Trisphosphate ◽

Inositol Tetrakisphosphate ◽

Cortex Slices

The effects of Li+ on carbachol-stimulated phosphoinositide metabolism were examined in rat cerebral-cortex slices labelled with myo-[2-3H]inositol. The muscarinic agonist carbachol evoked an enhanced steady-state accumulation of [3H]inositol monophosphate ([3H]InsP1), [3H]inositol bisphosphate ([3H]InsP2), [3H]inositol 1,3,4-trisphosphate ([3H]Ins(1,3,4)P3), [3H]inositol 1,4,5-trisphosphate ([3H]Ins(1,4,5)P3) and [3H]inositol tetrakisphosphate ([3H]InsP4). Li+ (5 mM), after a 10 min lag, severely attenuated carbachol-stimulated [3H]InsP4 accumulation while simultaneously potentiating accumulation of both [3H]InsP1 and [3H]InsP2 and, at least initially, of [3H]Ins(1,3,4)P3. These data are consistent with inhibition of inositol mono-, bis- and 1,3,4-tris-phosphate phosphatases to different degrees by Li+ in brain, but are not considered to be completely accounted for in this way. Potential direct and indirect mechanisms of the inhibitory action of Li+ on [3H]InsP4 accumulation are considered. The present results stress the complex action of Li+ on cerebral inositol metabolism and indicate that more complex mechanisms than are yet evident may regulate this process.

Download Full-text