Inositol-trisphosphate 3-kinase
Inositol (1,4,5) trisphosphate 3-kinase (EC 2.7.1.127), abbreviated here as ITP3K, is an enzyme that facilitates a phospho-group transfer from adenosine triphosphate to 1D-myo-inositol 1,4,5-trisphosphate. This enzyme belongs to the family of transferases, specifically those transferring phosphorus-containing groups (phosphotransferases) with an alcohol group as acceptor. The systematic name of this enzyme class is ATP:1D-myo-inositol-1,4,5-trisphosphate 3-phosphotransferase. ITP3K catalyzes the transfer of the gamma-phosphate from ATP to the 3-position of inositol 1,4,5-trisphosphate to form inositol 1,3,4,5-tetrakisphosphate. ITP3K is highly specific for the 1,4,5-isomer of IP3, and it exclusively phosphorylates the 3-OH position, producing Ins(1,3,4,5)P4, also known as inositol tetrakisphosphate or IP4.
| Inositol trisphosphate 3-kinase | |||||||||
|---|---|---|---|---|---|---|---|---|---|
Inositol-trisphosphate 3-kinase A Catalytic Core. 1TZD | |||||||||
| Identifiers | |||||||||
| EC no. | 2.7.1.127 | ||||||||
| CAS no. | 106283-10-7 | ||||||||
| Databases | |||||||||
| IntEnz | IntEnz view | ||||||||
| BRENDA | BRENDA entry | ||||||||
| ExPASy | NiceZyme view | ||||||||
| KEGG | KEGG entry | ||||||||
| MetaCyc | metabolic pathway | ||||||||
| PRIAM | profile | ||||||||
| PDB structures | RCSB PDB PDBe PDBsum | ||||||||
| Gene Ontology | AmiGO / QuickGO | ||||||||
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In biology, the enzyme ITP3K is abbreviated a number of different ways, including 1D-myo-inositol-trisphosphate 3-kinase, ITP3K, ITPK, IP3-kinase, IP3-3-kinase, Ins(1,4,5)P3 3-kinase. In addition the enzyme may be named as the product of one of 3 genes in humans ITPKA, ITPKB, and ITPKC, or one of two in fruit flies, IP3K1 and IP3K2—a mutant known to geneticists as wavy. The nematode genome has one form of the enzyme, coded by the LFE-2 gene. ITP3K enzymes are expressed only in metazoans; they are not expressed in yeast or plants.
All ITP3Ks belong to a larger structural family, the inositol polyphosphate kinases, or IPKs. Note however, that the human genome also contains a gene for a different kinase known as ITPK1, which is an inositol 1, 3, 4-trisphosphate 5/6-kinase and is not a member of the IPK family.
The ITP3K enzyme family is sometimes confused with a different enzyme family that has a similar name, that is, the phosphatidyl inositol 3-kinases or phosphoinositide 3-kinase (PI3-K),whose substrates are inositol lipids, not the soluble second messenger inositol trisphosphate.