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Studies of Rat Brain Choline Ethanolamine Phosphotransferases Using Labeled Alkylacylglycerol as Substrate with Evidence for Reversibility of the Reactions

  • Gianfrancesco Goracci
  • Lloyd A. Horrocks
  • Giuseppe Porcellati
Part of the Advances in Experimental Medicine and Biology book series (AEMB, volume 101)

Abstract

Phosphotransferases have been thoroughly reviewed by Van den Bosch (1974). These enzymes transfer phosphocholine or phosphoethanolamine from a cytidine nucleotide to a diglyceride to form a phosphoglyceride and CMP. For the brain enzymes, new developments are reviewed by Freysz et al. (1978) in this volume. In nearly all studies of the phosphotransferases, activities have been assayed by measuring the incorporation of radioactivity from CDP-choline or CDP-ethanolamine. Mudd et al. (1969) showed that radioactive 1,2diacyl-sn-glycerols were incorporated into phosphatidyl choline by rat liver microsomes. Radioactive 1,2-diacyl-sn-glycerols are also incorporated into phosphatidyl ethanolamine by rat liver microsomes (De Kruyff et al. 1970). The choline phosphotransferase was more active than the ethanolamine phosphotransferase. Kanoh (1970) used a variety of labeled 1,2-diacyl-sn-glycerols and concluded that the phosphotransferases in liver microsomes have very little selectivity for molecular species with the exception of a preference for hexaenoic species by ethanolamine phosphotransferase. The cholinephosphotransferase in spinach leaves incorporates labeled 1,2-diacyl-sn-glycerols into phosphatidyl choline (Devor and Mudd, 1971). These results prove that 1,2-diacyl-sn-glycerols and the CDP-nucleotide are the direct substrates of the phosphotransferases. Although incorporation into glycerophospholipids is always measured, the production of CMP is generally assumed. The phosphotransferases in liver are reversible (Kanoh and Ohno, 1973). Incubation of rat liver microsomes with CMP resulted in release of CDP-choline and CDPethanolamine. For the reverse reactions, choline phosphotransferase was more active than ethanolamine phosphotransferase.

Keywords

Microsomal Protein Ethanolamine Glycerophospholipids Choline Phosphoglycerides Ethanolamine Phosphoglycerides Choline Phosphotransferase 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Plenum Press, New York 1978

Authors and Affiliations

  • Gianfrancesco Goracci
    • 1
  • Lloyd A. Horrocks
    • 2
  • Giuseppe Porcellati
    • 1
  1. 1.Istituto di Chimica Biologica, Facoltà di MedicinaUniversità di Perugia, Policlinico MontelucePerugiaItaly
  2. 2.Department of Physiological ChemistryThe Ohio State UniversityColumbusUSA

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