Headgroups inositol

Figure 1. Phosphoiylation, dephosphorylation and cleavage of Ptdlns. PI3-K phosphorylates the inositol ring at D3, while PTEN dephosphotylates it at the same position. SHIP dephosphotylates 5-phosphotylated Ptdlns, PLOy hydrolyses the phosphodiester bond between the glycerol backbone and the inositol headgroup of Ptdlns (3,4)/ 2> releasing IP3.

Ptdlns 4,5-P2 is formed by a two-stage phosphorylation of Ptdlns, which is first phosphorylated at the 4-position of its inositol headgroup by a specific kinase to form Ptdlns 4-P this is in turn phosphorylated at the 5-position to give Ptdlns 4,5-P2, the substrate for receptor-mediated lipid hydrolysis. As well as the two kinases responsible for the stepwise phosphorylation of Ptdlns there are corresponding phospho-... 

Better studied are the chemotaxis signaling events triggered by the liberated / 7 subunits upon GPCR-catalyzed dissociation of the G protein (Fig. 3). In the current model, the (3 complex directly docks to and activates phosphatidylinositol-3-kinase 7 (PI3K7), a membrane-associated enzyme that phosphorylates the inositol headgroup of phosphatidylinositol... 

The total synthesis of a novel hybrid lipid Pea-PIP2 (51), possessing a phosphatidyl ethanolamine (PE) headgroup at the 1-position and a phosphatidyl inositol 4,5-bisphosphate [PtdIns(4,5)P2] headgroup at the 4-position has been elaborated. Reporter groups (biotin, fluorophores, spin label) were... 

There are multiple phospholipase C s (PLCs) that are linked via G-proteins to neurotransmitter receptors. PLCs split the link between the Sn3 carbon and the phosphorus, thus generating two molecules the headgroup phosphate and diacylglycerol (DAG). PLCs particularly act on inositol phospholipids, generating inositol phosphates and DAG. As in the PLA2 cycle, both of these products are active signal transduction molecules. Again, the cycle must be terminated as shown in Fig. 2, by means of inositol phosphatases and DAG kinases. 

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