User:Foreignbubblez/Inositol phosphate

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Inositol phosphates are a group of mono- to hexaphosphorylated inositols. Each form of inositol phosphate is distinguished by the number and position of the phosphate group on the inositol ring.


 * inositol monophosphate (IP)
 * inositol bisphosphate (IP2)
 * inositol triphosphate (IP3)
 * inositol tetraphosphate (IP4)
 * inositol pentakisphosphate (IP5)
 * inositol hexaphosphate (IP6) also known as phytic acid, or phytate (as a salt).

A series of phosphorylation and dephosphorylation reactions are carried out by at least 19 phosphoinositide kinases and 28 phosphoinositide phosphatase enzymes allowing for inter-conversion between the compounds based on cellular demand.

Inositol Phosphates can either be soluble or insoluble depending on their chemical structure. Insoluble inositol phosphates are often referred to as phosphoinositides or PtdInsP and can be found associated with sub-cellular membranes or in nuclear subdomains. PIP2 (also known as PtdIns(4,5)P2) is found to be hydrophobic in nature and thus remains attached to the plasma membrane in the cell. Soluble inositol phosphates such as IP3 (Ins(1,4,5)P3) are able to dissolve in the cytoplasm of cells contributing to its crucial role as a secondary messenger in signal transduction pathways.

Inositol phosphates play a crucial role in various signal transduction pathways responsible for cell growth and differentiation, apoptosis, DNA repair, RNA export, regeneration of ATP and more.

Inositol triphosphate
Main article: Inositol triphosphate

The inositol-phospholipid signaling pathway is responsible for the generation of IP3 through the cleavage of Phosphatidylinositol 4,5-bisphosphate (PIP2) found in the lipid bilayer of the plasma membrane via G proteins (Gq) and phospholipase C-β. Soluble Ip3 is able to rapifly diffuse into the cytsol and bind to the inositol triphosphate receptor (InsP3Rs) located in the endoplasmic reticulum. High concentrations of calcium will be released from the endoplasmic reticulum as a result, serving as a rapid and potent signal for various cellular processes. Here, IP3 is functioning as a secondary messenger responsible for activating the InsP3Rs which serve as a connection point for multiple signal transduction pathways.

Further reading: Function of calcium in humans