Influence of Ca2+ and Mg2+ on the turnover of the phosphomonoester group of phosphatidylinositol 4-phosphate in human erythrocyte membranes. 1987

H Hegewald, and E Müller, and R Klinger, and R Wetzker, and H Frunder
Institute of Biochemistry, Friedrich-Schiller-University, Jena, German Democratic Republic.

In isolated erythrocyte membranes, increasing the free Mg2+ concentration from 0.5 to 10 mM progressively activates the membrane-bound phosphatidylinositol (PtdIns) kinase and leads to the establishment of a new equilibrium with higher phosphatidylinositol 4-phosphate (PtdIns4P) and lower PtdIns concentrations. The steady-state turnover of the phosphomonoester group of PtdIns4P also increases at high Mg2+ concentrations, indicating a simultaneous activation of PtdIns4P phosphomonoesterase by Mg2+. Half-maximum inhibition of PtdIns kinase occurs at 10 microM free Ca2+ in the presence of physiological free Mg2+ concentrations. Increasing free Mg2+ concentrations overcome Ca2+ inhibition of PtdIns kinase. In the presence of Ca2+, calmodulin activates Ca2+-transporting ATPase 5-fold, but does not alter pool size and radiolabelling of PtdIns4P. In intact erythrocytes, adding EGTA or EGTA plus Mg2+ and the ionophore A23187 to the external medium does not exert significant effects on concentration and radiolabelling of polyphosphoinositides when compared with controls in the presence of 1.4 mM free Ca2+.

UI MeSH Term Description Entries
D008274 Magnesium A metallic element that has the atomic symbol Mg, atomic number 12, and atomic weight 24.31. It is important for the activity of many enzymes, especially those involved in OXIDATIVE PHOSPHORYLATION.
D010716 Phosphatidylinositols 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. Inositide Phospholipid,Inositol Phosphoglyceride,Inositol Phosphoglycerides,Inositol Phospholipid,Phosphoinositide,Phosphoinositides,PtdIns,Inositide Phospholipids,Inositol Phospholipids,Phosphatidyl Inositol,Phosphatidylinositol,Inositol, Phosphatidyl,Phosphoglyceride, Inositol,Phosphoglycerides, Inositol,Phospholipid, Inositide,Phospholipid, Inositol,Phospholipids, Inositide,Phospholipids, Inositol
D010770 Phosphotransferases A rather large group of enzymes comprising not only those transferring phosphate but also diphosphate, nucleotidyl residues, and others. These have also been subdivided according to the acceptor group. (From Enzyme Nomenclature, 1992) EC 2.7. Kinases,Phosphotransferase,Phosphotransferases, ATP,Transphosphorylase,Transphosphorylases,Kinase,ATP Phosphotransferases
D002118 Calcium A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes. Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D002147 Calmodulin A heat-stable, low-molecular-weight activator protein found mainly in the brain and heart. The binding of calcium ions to this protein allows this protein to bind to cyclic nucleotide phosphodiesterases and to adenyl cyclase with subsequent activation. Thereby this protein modulates cyclic AMP and cyclic GMP levels. Calcium-Dependent Activator Protein,Calcium-Dependent Regulator,Bovine Activator Protein,Cyclic AMP-Phosphodiesterase Activator,Phosphodiesterase Activating Factor,Phosphodiesterase Activator Protein,Phosphodiesterase Protein Activator,Regulator, Calcium-Dependent,AMP-Phosphodiesterase Activator, Cyclic,Activating Factor, Phosphodiesterase,Activator Protein, Bovine,Activator Protein, Calcium-Dependent,Activator Protein, Phosphodiesterase,Activator, Cyclic AMP-Phosphodiesterase,Activator, Phosphodiesterase Protein,Calcium Dependent Activator Protein,Calcium Dependent Regulator,Cyclic AMP Phosphodiesterase Activator,Factor, Phosphodiesterase Activating,Protein Activator, Phosphodiesterase,Protein, Bovine Activator,Protein, Calcium-Dependent Activator,Protein, Phosphodiesterase Activator,Regulator, Calcium Dependent
D004910 Erythrocyte Membrane The semi-permeable outer structure of a red blood cell. It is known as a red cell 'ghost' after HEMOLYSIS. Erythrocyte Ghost,Red Cell Cytoskeleton,Red Cell Ghost,Erythrocyte Cytoskeleton,Cytoskeleton, Erythrocyte,Cytoskeleton, Red Cell,Erythrocyte Cytoskeletons,Erythrocyte Ghosts,Erythrocyte Membranes,Ghost, Erythrocyte,Ghost, Red Cell,Membrane, Erythrocyte,Red Cell Cytoskeletons,Red Cell Ghosts
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D018129 Phosphatidylinositol Phosphates Phosphatidylinositols in which one or more alcohol group of the inositol has been substituted with a phosphate group. Polyphosphoinositides,Phosphatidyl Inositol Phosphates,Polyphosphoinositide,Inositol Phosphates, Phosphatidyl,Phosphates, Phosphatidyl Inositol,Phosphates, Phosphatidylinositol
D019269 Phosphatidylinositol 4,5-Diphosphate 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. (Kendrew, The Encyclopedia of Molecular Biology, 1994) PtdInsP2,Phosphatidylinositol 4,5-Biphosphate,Phosphatidylinositol Phosphate, PtdIns(4,5)P2,Phosphatidylinositol-4,5-Biphosphate,PtIns 4,5-P2,PtdIns(4,5)P2,PtdInsP,4,5-Biphosphate, Phosphatidylinositol,4,5-Diphosphate, Phosphatidylinositol,Phosphatidylinositol 4,5 Biphosphate,Phosphatidylinositol 4,5 Diphosphate
D019870 1-Phosphatidylinositol 4-Kinase An enzyme that catalyzes the conversion of phosphatidylinositol (PHOSPHATIDYLINOSITOLS) to phosphatidylinositol 4-phosphate, the first committed step in the biosynthesis of phosphatidylinositol 4,5-bisphosphate. Phosphatidylinositol 4-Kinase,PtdIns 4-Kinase,PI 4-Kinase,Phosphatidylinositiol Kinase,Phosphatidylinositol Kinase Type II,Phosphoinositide Kinase,1 Phosphatidylinositol 4 Kinase,Kinase, Phosphatidylinositiol,Kinase, Phosphoinositide,PI 4 Kinase,Phosphatidylinositol 4 Kinase,PtdIns 4 Kinase

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