Inositol trisphosphate

1D-myo-inositol 1,4,5-triphosphate

The inositol trisphosphate trianion
Names
IUPAC name (1R,2R,3S,4R,5R,6S)-3,5,6-Trihydroxy-1,2,4-cyclohexanetriyl tris[dihydrogen (phosphate)]
Other names IP3; Triphosphoinositol; Inositol 1,4,5-trisphosphate
Identifiers
CAS Number	85166-31-0
3D model (Jmol)	Interactive image
ChemSpider	388562
IUPHAR/BPS	4222
PubChem CID	439456
InChI InChI=1S/C6H15O15P3/c7-1-2(8)5(20-23(13,14)15)6(21-24(16,17)18)3(9)4(1)19-22(10,11)12/h1-9H,(H2,10,11,12)(H2,13,14,15)(H2,16,17,18)/t1-,2+,3+,4-,5-,6-/m1/s1 Key: MMWCIQZXVOZEGG-XJTPDSDZSA-N InChI=1/C6H15O15P3/c7-1-2(8)5(20-23(13,14)15)6(21-24(16,17)18)3(9)4(1)19-22(10,11)12/h1-9H,(H2,10,11,12)(H2,13,14,15)(H2,16,17,18)/t1-,2+,3+,4-,5-,6-/m1/s1 Key: MMWCIQZXVOZEGG-XJTPDSDZBF
SMILES [C@H]1([C@@H]([C@H]([C@@H]([C@H]([C@@H]1OP(=O)(O)O)O)OP(=O)(O)O)OP(=O)(O)O)O)O
Properties
Chemical formula	C6H15O15P3
Molar mass	420.096 g/mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Inositol trisphosphate or inositol 1,4,5-trisphosphate (also commonly known as triphosphoinositol; abbreviated InsP₃ or Ins3P or IP₃), together with diacylglycerol (DAG), is a secondary messenger molecule used in signal transduction and lipid signaling in biological cells. While DAG stays inside the membrane, IP₃ is soluble and diffuses through the cell. It is made by hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP₂), a phospholipid that is located in the plasma membrane, by phospholipase C (PLC).

IP₃ is an organic molecule with a molecular mass of 420.10 g/mol. Its empirical formula is C₆H₁₅O₁₅P₃. It is composed of an inositol ring with three phosphate groups bound at the 1, 4, and 5 carbon positions, and three hydroxyl groups bound at positions 2, 3, and 6.

Phosphate groups can exist in three different forms depending on a solution's pH. Phosphorus atoms can bind three oxygen atoms with single bonds and a fourth oxygen atom using a double/dative bond. The pH of the solution, and thus the form of the phosphate group determines its ability to bind to other molecules. The binding of phosphate groups to the inositol ring is accomplished by phosphor-ester binding (see phosphoric acids and phosphates). This bond involves combining a hydroxyl group from the inositol ring and a free phosphate group through a dehydration reaction. Considering that the average physiological pH is approximately 7.4, the main form of the phosphate groups bound to the inositol ring in vivo is PO₄²⁻. This gives IP₃ a net negative charge, which is important in allowing it to dock to its receptor, through binding of the phosphate groups to positively charged residues on the receptor. IP₃ has three hydrogen bond donors in the form of its three hydroxyl groups. The hydroxyl group on the 6th carbon atom in the inositol ring is also involved in IP₃ docking.