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style="background: #F8EABA; text-align: center;" colspan="2" Inositol triphosphate
CAS number 85166-31-0
PubChem 55310
Molecular formula C6H15O15P3
Molar mass 420.096
style="background: #F8EABA; text-align: center;" colspan="2" Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

Inositol trisphosphate or inositol 1,4,5-trisphosphate (also commonly known as triphosphoinositol; abbreviated InsP3 or IP3), together with diacylglycerol, is a second messenger molecule used in signal transduction in biological cells. It is made by hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2), a phospholipid that is located in the plasma membrane, by phospholipase C.

Its main functions are to mobilize Ca2+ from storage organelles and to regulate cell proliferation and other cellular reactions. For example, in the fruit fly Drosophila, InsP3 is used for intracellular transduction of light recognition in eye cells.

In smooth muscle cells, IP3 binds to and activates the InsP3 receptor on the membrane of the sarcoplasmic reticulum (SR) opens a calcium channel, resulting in the release of Ca2+ into the sarcoplasm[1]. This increase in Ca2+ activates the ryanodine receptor-operated channel on the SR, leading to a further increase in the Ca2+ concentration in the muscle cell, resulting in the contraction of the muscle cell[2].

Inositol tetra-, penta-, and hexa-phosphates have been implicated in gene expression by Shen[3] and Steger[4] (both in Science Magazine).

See also

External links


  1. Ferris CD, Snyder SH. IP3 receptors. Ligand-activated calcium channels in multiple forms. Adv Second Messenger Phosphoprotein Res. 1992;26:95-107. PMID 1329896
  2. Somlyo AP, Somlyo AV. Signal transduction and regulation in smooth muscle. Nature. 1994 Nov 17;372(6503):231-6. PMID 7969467
  3. Shen X, et al. Modulation of ATP-dependent chromatin-remodeling complexes by inositol polyphosphates. Science. 2003 Jan 3;299(5603):112-4. PMID 12434013
  4. Steger DJ, et al. Regulation of chromatin remodeling by inositol polyphosphates. Science. 2003 Jan 3;299(5603):114-6. PMID 12434012


pl:Trifosforan inozytolu
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