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Phosphatidylinositol (abbreviated PtdIns, or PI) is a negatively charged phospholipid and a minor component in the cytosolic side of eukaryotic cell membranes.

The phosphatidylinositol can be phosphorylated to form phosphatidylinositol phosphate (PIP), phosphatidylinositol bisphosphate (PIP₂) and phosphatidylinositol trisphosphate (PIP₃). PIP, PIP₂ and PIP₃ are collectively called phosphoinositides.

Biosynthesis

Biosynthesis of phosphatidylinositol catalyzed by phosphatidylinositol synthase. Figure adapted from Christopher, K.; van Holde, K.E.; Ahern, Kevin G. Biochemistry Third Edition. Pearson Education, Inc: Singapore, 2005; p 678.^[1]

The synthesis of phosphatidylinositol is catalyzed by phosphatidylinositol synthase and involves CDP-diacylglycerol and L-myo-inositol.^[1]

Chemistry

PI has a polar and non-polar region, making the lipid an amphiphile. Amphiphatic lipids demonstrate polymorphic behavior, a current academic research topic. Phosphatidylinositol is classified as a glycerophospholipid that contains a glycerol backbone, two non-polar fatty acid tails, a phosphate group substituted with an inositol polar head group.

The most common fatty acids of phosphoinositides are stearic acid in the SN₁ position and arachidonic acid, in the SN₂ position. Hydrolysis of phosphoinositides yield one mole of glycerol, two moles of fatty acids, one mole of inositol and one, two, or three moles of phosphoric acids, depending on the number of phosphates on the inositol rings. Phosphoinositides are regarded as the most acidic phospholipid.

Phosphoinositides

Phosphorylated forms of phosphatidylinositol are called phosphoinositides and play important roles in lipid signaling, cell signaling and membrane trafficking. The inositol ring can be phosphorylated by a variety of kinases on the three, four and five hydroxyl groups in seven different combinations. However, the two and six hydroxyl group is typically not phosphorylated due to steric hindrance.

All seven variations of the following phosphoinositides have been found in animals:

Phosphatidylinositol monophosphates:

Phosphatidylinositol 3-phosphate, also known as PtdIns3P or PI(3)P
Phosphatidylinositol 4-phosphate, also known as PtdIns4P or PI(4)P
Phosphatidylinositol 5-phosphate, also known as PtdIns5P or PI(5)P

Phosphatidylinositol bisphophosphates:

Phosphatidylinositol 3,4-bisphosphate, also known as PtdIns(3,4)P or PI(3,4)P₂
Phosphatidylinositol 3,5-bisphosphate, also known as PtdIns(3,5)P or PI(3,5)P₂
Phosphatidylinositol 4,5-bisphosphate, also known as PtdIns(4,5)P, PI(4,5)P₂ or often simply referred to as PIP₂

Phosphatidylinositol trisphophosphate:

Phosphatidylinositol 3,4,5-trisphosphate, also known as PtdIns(3,4,5)P or PI(3,4,5)P₃

These phosphoinositides are also found in plant cells, with the exception of PIP₃.^[2]

References

^ ^a ^b Mathews, Chrisotphe K.; van Holde, K.E.; Ahern, Kevin G., (2005). Biochemistry Third Edition.
^ Muller-Roeber B, Pical C; , (2002). Inositol Phospholipid Metabolism in Arabidopsis. Characterized and Putative Isoforms of Inositol Phospholipid Kinase and Phosphoinositide-Specific Phospholipase C.

Additional images

Membrane lipids
Phosphatidyl-inositol
Inositol
Glycerol

External links

MeSH Phosphatidylinositols
Phosphatidylinositol at Lipid Library

UpToDate Contents

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English Journal

Regulation of insulin signaling in skeletal muscle by PIP3 phosphatase, SKIP, and endoplasmic reticulum molecular chaperone glucose-regulated protein 78.

Ijuin T1, Hatano N2, Hosooka T3, Takenawa T4.
Biochimica et biophysica acta.Biochim Biophys Acta.2015 Dec;1853(12):3192-201. doi: 10.1016/j.bbamcr.2015.09.009. Epub 2015 Sep 14.
Insulin resistance is characterized as a pathogenic factor in type 2 diabetes. Despite skeletal muscle being primarily responsible for systemic glucose disposal, the mechanisms underlying the induction of insulin resistance in skeletal muscle have not been fully elucidated. A number of studies have
PMID 26376412

Streptomyces bambusae sp. nov., Showing Antifungal and Antibacterial Activities, Isolated from Bamboo (Bambuseae) Rhizosphere Soil Using a Modified Culture Method.

Nguyen TM1, Kim J2.
Current microbiology.Curr Microbiol.2015 Dec;71(6):658-68. doi: 10.1007/s00284-015-0899-2. Epub 2015 Sep 2.
Strain T110(T) was isolated from a bamboo rhizosphere soil sample in the Republic of Korea and was found to produce antibiotics and secondary metabolites against a broad range of bacterial and fungal pathogens. It is a gram-positive actinobacterium with a straight and smooth, spore chain morphology.
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MicroRNA-155 Regulates ROS Production, NO Generation, Apoptosis and Multiple Functions of Human Brain Microvessel Endothelial Cells Under Physiological and Pathological Conditions.

Liu Y1, Pan Q1, Zhao Y2, He C1, Bi K1, Chen Y1, Zhao B1, Chen Y1,2, Ma X1.
Journal of cellular biochemistry.J Cell Biochem.2015 Dec;116(12):2870-81. doi: 10.1002/jcb.25234.
The microRNA-155 (miR155) regulates various functions of cells. Dysfunction or injury of endothelial cells (ECs) plays an important role in the pathogenesis of various vascular diseases. In this study, we investigated the role and potential mechanisms of miR155 in human brain microvessel endothelial
PMID 26012521

Japanese Journal

腎臓がんに対する新規分子標的薬の開発 (特集婦人科がん・泌尿器がん)

三浦裕司,高野利実
腫瘍内科 = Clinical oncology 16(2), 137-142, 2015-08
NAID 40020571487

Phosphatidylinositol 4-kinase Ⅲ beta is the target of oxoglaucine and pachypodol (Ro 09-0179) for their anti-poliovirus activities, and is located at upstream of the target step of brefeldin A

Arita Minetaro,Philipov Stefan,Galabov Angel S.
Microbiology and immunology 59(6), 338-347, 2015-06
NAID 40020510073

Alterations in Intestinal Permeability Cause Colonic Inflammation and Fibrosis in Type III Phosphatidylinositol Phosphate Kinase-Deficient Mice

NAKAMURA Ryotaro,TAKASUGA Shunsuke,HORIE Yasuo,SASAKI Takehiko
秋田医学 41(3-4), 129-135, 2015-03-31
… We recently established mice lacking the type III phosphatidylinositol phosphate kinase gene(PipkIII) in enterocytes, which represent a unique model of intestinal inflammation associatedwith extensive fibrosis that closely resembles human Crohn's disease. …
NAID 120005616171

Related Pictures

Membrane lipid asymmetry - MBInfo Wiki Phosphatidylinositols; Inositol Phosphoglycerides; Phosphoinositides; PtdIns Kevin Ahern's Biochemistry (BB 451/551) at Oregon State University Class III Phosphatidylinositol 3-Kinases; Phosphatidylinositol 3-Kinase, Class III Phosphatidylinositol chemical structure, molecular structures of lipids, isolated on File:Phosphatidylinositol.jpg Phosphatidylinositol - Wikipedia Phosphatidylinositol | CAS 383907-36-6 | Santa Cruz Biotech

★リンクテーブル★

リンク元	「phosphoinositide」「PtdIns」「ホスファチジルイノシトール」「フォスファチジルイノシトール」「inositol phospholipid」
拡張検索	「glycosylphosphatidylinositol diacylglycerol-lyase」「phosphatidylinositol 4-kinase」「1-phosphatidylinositol 4-kinase」

「phosphoinositide」

Phosphatidylinositol
	Other names PI, PtdIns
Properties
Molecular formula	C47H83O13P
Molar mass	886.56 g/mol, neutral with fatty acid composition - 18:0, 20:4
	(verify) (what is: /?); Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
	Infobox references