THE SYNTHESIS OF CHOLINE AND ETHANOLAMINE PHOSPHOGLYCERIDES IN NEURONAL AND GLIAL CELLS OF RABBIT IN VITRO¹

Abstract

Abstract— The de novo synthesis of phosphatidylcholine and phosphatidylethanolamine in isolated neuronal and glial cells from adult rabbit brain cortex was investigated in vitro, using labelled phosphorylcholine (phosphorylethanolamine) or cytidine‐5′‐phosphate choline (cytidine‐5′‐phosphate ethanolamine), as lipid precursors. Synthesis of phospholipid from phosphorylcholine and phosphorylethanolamine in both fractions was extremely low when compared to that derived from the corresponding cytidine nucleotides. The neuronal cell‐enriched fraction was found to possess a much higher rate of synthesis of both lipids from all precursors. Neuronal/glial ratios of about 5–9 were found for the synthesis of phosphatidylcholine and phosphatidylethanolamine from cytidine‐5′‐phosphate choline and cytidine‐5′‐phosphate ethanolamine, respectively. Several kinetic properties of the choline‐phosphotransferase (EC 2.7.8.2) and ethanolaminephosphotransferase (EC 2.7.8.1) were found to be similar both in neurons and in glia (e.g. Km of cytidine‐5′‐phosphate ethanolamine, Km of diacyl glycerol, pH optimum, need for divalent cations), but the Km value for cytidine‐5′‐phosphate choline in glial cells was much lower (2.3 × 10−4m) than in neurons (1 × 10−3m). The Kmfor cytidine‐5′‐phosphate ethanolamine in both cells was much lower than in whole brain microsomes. It is concluded that the cytidine‐dependent enzymic system for phosphatidylcholine and phosphatidylethanolamine synthesis is concentrated mostly in the neuronal cells, as compared to glia.

Enzymic synthesis of ethanolamine plasmalogens through ethanolaminephosphotransferase activity in neurons and glial cells of rabbit in vitro

“…1). Somewhat similar findings were observed for diacyl-GPE synthesis (1). During the incubation period of 30 rain, formation of products (diacyl-GPE or alkenylacyl-GPE) from CDPE was proportional to the amount of neuronal or glial protein over the range from 0.5-2.0 mg/ml.…”

“…Neuronal and glial cells have been studied recently in vitro in a variety of biochemical reactions (1), including protein synthesis (2). No reports have as yet appeared, however, on the ability of these cells to perform phospholipid biosynthesis, except for some studies on the base-exchange reaction (3)(4)(5) and on the synthesis of 1,2-diacyl-sn-glycero-3-phosphorylcholine 1presented in part at the IXth International Congress of Biochemistry, Stokholm, July 1973 and at the XIXth National Meeting of Biochemistry, Trieste, October 1973.…”

The Synthesis of Choline Phosphoglycerides in the Giant Fibre System of the Squid

“…The identified spots were scraped off the plate and eluted several times with chloroform-methanol-acetic acid-water (50: 39: 1 : 10, by vol). Eluates were dried under a stream of nitrogen in counting vials and counted according to BINAGLIA et al (1973) in a Model 3375 Packard liquid scintillation spectrometer, using the external standard method for quench correction. With control experiments it was observed that nearly all the original radioactivity of pure reference standards could be recovered by using this procedure.…”

Evidence for the Presence of CDP‐Ethanolamine: 1,2‐diacyl‐sn‐glycerol Ethanolaminephosphotransferase in Rat Central Nervous System Myelin

“…We have found evidence for the presence of CDP-ethanolamine: 1,2diacyl-sn-glycerol ethanolaminephosphotransferase (EC 2.7.8.1), which catalyzes the last step in the biosynthesis of phosphatidylethanolamine and related ethanolamine glycerophospholipids (Kennedy and Weiss, 1956). Its presence in nervous tissue has been well documented (Porcellati et al, 1970;Ansell and Metcalfe, 1971; Radominska-Pyrek and Horrocks, 1972;Binaglia et al, 1973;Roberti et al, 1975;Freysz et al, 1977;Radominska-Pyrek et al, 1977;Dreyfus et al, 1978).…”