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Cholinephosphotransferase activity in human platelets |
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| Authors: | Goracci Gianfrancesco Gresele Paolo Giuseppe Arienti Patrizia Porrovecchio Giuseppe G. Nenci Giuseppe Porcellati |
| Affiliation: | 1. Istituto di Chimica Biologica, The Medical School, University of Perugia, Policlinico Monteluce, 06100, Perugia, Italy 2. Istituto di Semeiotica Medica, The Medical School, University of Perugia, Policlinico Monteluce, 06100, Perugia, Italy |
| Abstract: | Disrupted human platelets possess a cholinephosphotransferase activity (EC 2.7.8.2) whose properties have been studied in this work. The labeling of choline glycerophospholipid (CGP) from radioactive cytidine-5'-diphosphate choline (CDP-choline) in vitro shows a maximum at pH 8.0 (using Hepes [4-(2-hydroxyethyl)-piperazine-1-ethane-2-sulfonic acid] as a buffer) and is stimulated by Mn2+, Mg2+ and diacylglycerol. The enzymic activity is inhibited by Ca2+. The dependence of human platelet cholinephosphotransferase upon CDP-choline concentration does not follow the Michaelis-Menten equation. CMP strongly inhibits the reaction. The functional implications of this newly discovered platelet activity are briefly considered. |
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