| phosphatidylinositol | <biochemistry> A phosphatidic acid combined with inositol found in biomembranes and a precursor to certain cellular signals. Sometimes referred to as inositide. It is a very important minor phospholipid in eukaryotes, involved in signal transduction processes. Contains myo inositol linked through the 1 hydroxyl group to phosphatidic acid. The 4 phosphate (PIP) and 4, 5 bisphosphate derivatives PIP2) are formed and broken down in membranes by the action of specific kinases and phosphatases (futile cycles). Signal sensitive phospholipase C enzymes remove the inositol moiety, in particular from 1,4,5 trisphosphate (PIP2) as inositol 1,4,5 triphosphate (Ins P3: IP3). Both the diacyl glycerol and products act as second messengers. Synonym: phosphoinositide. (20 Sep 2002) |
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| phosphatidylinositol 4,5-bisphosphate | <biochemistry> This is a molecule of phosphatidylinositol with two additional sites of phosphorylation. It is an important constituent of cell membrane phospholipids as well as a precursor of the second messengers, diacylglycerol and inositol 1,4,5-trisphosphate. Acronym: PIP2 (20 Sep 2002) |
| phosphatidylinositol 4,5-bisphosphate kinase | <enzyme> Membrane-associated enzyme Registry number: EC 2.7.1.- Synonym: ptdins 4,5-p2 kinase, phosphatidylinositol 4,5-bisphosphate kinase, ptdins(4,5)p2 3oh-kinase (26 Jun 1999) |
| phosphatidylinositol 4,5-diphosphate | <biochemistry> A phosphoinositide present in all eukaryotic cells, particularly in the plasma membrane. It is the major substrate for receptor-stimulated phosphoinositidase c, with the consequent formation of inositol 1,4,5-triphosphate and diacylglycerol, and probably also for receptor-stimulated inositol phospholipid 3-kinase. (12 Dec 1998) |
| phosphatidylinositol 4-phosphate | <biochemistry> The intermediate in the biosynthesis of phosphatidylinositol 4,5-bisphosphate from phosphatidylinositol. (20 Sep 2002) |
| phosphatidylinositol 4-phosphate phosphatase | <enzyme> From human erythrocyte membranes Registry number: EC 3.1.3.- Synonym: ptdins-4p-phosphatase, phosphatidylinositol-4-phosphate monoesterase, ptdins4p monoesterase (26 Jun 1999) |
| phosphatidylinositol phosphates | <biochemistry> Phosphatidylinositols in which one or more alcohol group of the inositol has been substituted with a phosphate group. (12 Dec 1998) |
| phosphatidylinositol synthase | <enzyme> An enzyme that catalyses the reaction of CDP-diacylglycerol with inositol to form CMP and phosphatidylinositol; found in the endoplasmic reticulum. (20 Sep 2002) |
| phosphatidylinositol-3,4,5-trisphosphate 5-phosphatase | <enzyme> Hydrolyzes the 5-position phosphate of ptdins(3,4,5)p3 forming phosphatidylinositol-3,4-bisphosphate; an isoenzyme forms a complex with the p85/p110 form of pi 3-kinase Registry number: EC 3.1.3.- Synonym: ptdins(3,4,5)p3 5-phosphatase, pi(3,4,5)p3 5-pase (26 Jun 1999) |
| phosphatidylinositol-3-phosphatase | <enzyme> Hydrolyzes phosphatidylinositol 3-phosphate in nih 3t3 cells; specific as it has little or no activity on the monoester phosphates of ptdins(4)p, ptdins(4,5)p2, or inositol 1,3-bisphosphate; does not require added metal ions for activity and is maximally active in the presence of edta; inhibited by ca(2+), mg(2+),zn(2+), and the phosphatase inhibitor vo(3-)4 Registry number: EC 3.1.3.64 Synonym: phosphatidylinositol 3-phosphatase (26 Jun 1999) |
| phosphatidylinositol-ceramide phosphoinositol transferase | <enzyme> Involved in biosynthesis of inositol-containing sphingolipids; isolated from saccharomyces cerevisiae Registry number: EC 2.4.1.- Synonym: ipc synthase (26 Jun 1999) |
| phosphatidylinositols | <biochemistry> Derivatives of phosphatidic acids in which the phosphoric acid is bound in ester linkage to the hexahydroxy alcohol, myo-inositol. Complete hydrolysis yields 1 mole of glycerol, phosphoric acid, myo-inositol, and 2 moles of fatty acids. (12 Dec 1998) |
| N-acetylglucosaminyl-phosphatidylinositol de-N-acetylase | <enzyme> Involved in formation of glycosylphosphatidyl inositol membrane anchors in trypanosoma brucei; forms glucosaminyl-phosphatidylinositol Registry number: EC 3.5.1.- Synonym: glcnac-pi de-n-acetylase, pig-l protein, phosphatidylinositol glycan class l protein, n-acetylglucosaminyl-phosphatidylinositol deacetylase (26 Jun 1999) |
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| 1-phosphatidylinositol 3-kinase | <enzyme> An enzyme that catalyses the conversion of phosphatidylinositol to phosphatidylinositol 3-phosphate. This is the first committed step in the biosynthesis of phosphatidylinositol 3,4-bisphosphate and phosphatidylinositol 3,4,5-trisphosphate. This pathway is thought to play a critical role in DNA repair, v(d)j recombination and cell cyle checkpoints.37. Chemical name: ATP:1-phosphatidyl-1D-myo-inositol 3-phosphotransferase Registry number: EC 2.7.1.137 (12 Dec 1998) |
| 1-phosphatidylinositol 4-kinase | <enzyme> An enzyme that catalyses the conversion of phosphatidylinositol to phosphatidylinositol 4-phosphate, the first committed step in the biosynthesis of phosphatidylinositol 4,5-bisphosphate. Chemical name: ATP:1-phosphatidyl-1D-myo-inositol-4-phosphate Registry number: EC 2.7.1.67 (12 Dec 1998) |