- Inositol triphosphate
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CASNo = 85166-31-0
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PubChem = 55310
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Formula = C6H15O15P3
MolarMass = 420.096
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OtherCpds =Inositol trisphosphate or inositol 1,4,5-trisphosphate (also commonly known as triphosphoinositol; abbreviated InsP3 or IP3), together with diacylglycerol, is a
secondary messenger molecule used insignal transduction in biological cells. It is made byhydrolysis ofphosphatidylinositol 4,5-bisphosphate (PIP2), aphospholipid that is located in theplasma membrane , byphospholipase C .Mechanism
IP3 binds to and activates the InsP3 receptor on the membrane of the
endoplasmic reticulum (ER), andsarcoplasmic reticulum (SR) opens a calcium channel, resulting in the release of Ca2+ into thecytoplasm , andsarcoplasm respectively. [Ferris CD, Snyder SH. IP3 receptors. Ligand-activated calcium channels in multiple forms. Adv Second Messenger Phosphoprotein Res. 1992;26:95-107. PMID 1329896] This increase in Ca2+ activates theryanodine receptor -operated channel on the SR, leading to a further increase in the Ca2+.Function
Human
Its main functions are to mobilize Ca2+ from storage
organelle s and to regulatecell proliferation and other cellular reactions.In
smooth muscle cell s, for example, the increase in concentration of cytoplasmic calcium results in the contraction of the muscle cell. [Somlyo AP, Somlyo AV. Signal transduction and regulation in smooth muscle. Nature. 1994 Nov 17;372(6503):231-6. PMID 7969467] . "For further reading of Ca2+-mediated functions, seefunctions of calcium in humans ."Fruit fly
For example, in the fruit fly "Drosophila", InsP3 is used for intracellular transduction of light recognition in
eye cells.Sea urchin eggs
The slow block to polyspermy in the sea urchin is mediated by the phosphatidyl inositol diphosphate (PIP2) secondery messenger system. Activation of the binding receptors activates phospholipase C, witch cleaves PIP2 in the egg plasma membrane, releasing inositol triphosphate (IP3 into the egg cell cytoplasm. IP3 diffuses to the endoplasmic reticulum, where it opens calcium channels.
ee also
*
inositol
*inositol phosphate
*myo-inositol
*inositol pentakisphosphate
*inositol hexaphosphate
*inositol triphosphate receptor
*ITPR1
*ITPKC External links
*
References
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