The labeling of brain ethanolamine phosphoglycerides from cytidine diphosphate ethanolamine in vitro.

Abstract

AbstractChicken brain microsomes convert14C‐ethanolamine‐labeled cytidine diphosphate ethanolamine (CDPE) to ethanolamine lipids (EPG) at a measurable rate. Mitochondria and particle‐free supernatant fractions are almost inactive. On adding saturating amounts of diacyl glycerol to the microsomes, formation of EPG increases 10‐fold, and is almost totally confined to the diacylsn‐glycero‐3‐phosphorylethanolamine (GPE), whose synthesis increases 20‐fold (from 13.1 to 249 mμmoles/mg protein/hr). The addition of the 1‐alkenyl 2‐acyl glycerol also produces a noticeable increase in the rate of EPG labeling, which is almost exclusively confined to the alkenyl acyl GPE, whose synthesis is stimulated 30‐fold (from 3.1 to 90 mμmoles/mg protein/hr). Synthesis of alkyl acyl GPE from CDPE was not detected in the brain microsomes. Synthesis of EPG from CDPE by chicken brain homogenates has also been examined and results similar to those reported for the brain microsomes were obtained. In addition, small amounts of labeled alkyl acyl GPE are produced from CDPE in the homogenates, but in no case does this synthesis increase on adding various lipid acceptors to the incubation system. Various properties of the phosphorylethanolaminediacyl glycerol phosphotransferase (E.C. 2.7.8.1) of brain microsomes were examined. It is concluded that the enzymic activities which convert CDPE to diacyl GPE and alkenyl acyl GPE, respectively, are similar.