Phosphatidylinositol molecular species

DO THE MAIZE PHOSPHATIDYLINOSITOLPHOSPHATE-KINASE DISCRIMINATE BETWEEN THE PHOSPHATIDYLINOSITOL MOLECULAR SPECIES ... 

Figure 8 The composition of individual molecular species of phosphatidylinositol in mammalian surfactants as determined by mass spectrometry. Reproduced with permission from Postle AD, Heeley EL, and Wilton DC (2001) Comparative Biochemical Physiology,...

Phosphatidylcholine and phosphatidylinositol from rat liver were separated into molecular species under exactly the same conditions. Indeed, fractions identical in composition were obtained, although the relative proportions were rather different because of variations in fatty acid profiles, as expected. After modifying the mobile phase to 30 mM choline chloride in methanol-25 mM K2HP04-acetonitrile-acetic acid (90.5 7 2.5 0.8 by volume), molecular... 

We have recently shown [1] that phosphatidylinositol (PI) was synthesized mainly (or perhaps exclusively) in the endoplasmic reticulum and subsequently transferred to the plasma membrane of cells to allow the phosphoinositide cycle of signal transduction to proceed we have also shown that there is nearly the same quantitative distributions of PI molecular species in plasma membranes on one side and microsomes on the other side. In both membrane preparations [2, 3] the molecular species 16 0/18 2 was largely predominant (75-80 mol%). All other molecular species (16 0/18 3,18 2/18 2,18 1/18 2, 16 0/18 1, 18 0/18 2) presented percentages lower than 8%. However the question remained do the Pl-lanase and phosphatidylinositolphosphate (Plp)-kinase, which initiate the phosphoinositide cycle in plasma membranes, discriminate between the PI molecular species ... 

Chicha A., Justin A.-M., Jolliot A., Demandre C., Mazliak P. Biosynthesis of the molecular species of phosphatidylinositol found in microsomes and plasma membranes from etiolated maize coleoptiles. Plant Physiol Biochem.y 1993 31 507-513. 

The enzyme responsible for the final step of de novo biosynthesis of phosphatidylinositol (PI) is an endoplasmic reticulum enzyme the cytidine diphosphate-diacylglycerol (CDP-DAG) my< -inositol transferase (EC 2.7.8.11), or briefly PI-synthase. This enzyme catalyses the formation of PI and cytidine monophosphate (CMP) from CDP-DAG and myo-inosiiol [1], In a previous work [2], we found that the PI-synthase displayed a strong selectivity among the endogenous CDP-DAG molecular species used as substrates, in the microsomes from several plant tissues 16 0/18 2 and 16 0/18.3-CDP-DAG were markedly more utilized than other molecular species. Here, we are interested in the Pl-synthase selectivity among CDP-DAG molecular species, both when the enzyme was left within microsomal membranes or when it was solubilized and pre-purified. As a continuation of our work upon the solubilization of the Pl-synthase [3], we used CHAPS to solubilize the microsomal membranes as previously described. 

Justin AM, Mazliak P. Comparison of the molecular species patterns of phosphatidic acid, CDP-diacylglycerols and phosphatidylinositol in potato tuber, pea leaf and soyabean microsomes conseqences for the selectivity of the enzymes catalizing phosphatidylinositol biosynthesis. Biochim Biophys Acta 1992 1165 141-146. 

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