Biosynthesis of Sphingomyelin in Developing Brain Tissues

Abstract

The properties of the enzyme phosphorylcholine–ceramide transferase (CDP-choiine:ceramide cholinephosphotransferase, EC 2.7.8.3) which catalyzes the biosynthesis of sphingomyelin has been studied in brain tissues of the developing rat, chick, and calf. This enzyme catalyzes the transfer of the phosphorylcholine moiety from the coenzyme CDP-choline to the free primary hydroxyl group of threo-ceramides containing short-chain fatty acids in acyl linkage. Free erythro- or threo-sphingosines and erythro-ceramides with either short- or long-chain fatty acids in acyl linkage do not act as acceptors of phosphorylcholine in these tissues. In contrast to chicken liver these brain tissues do not catalyze the menadione-stimulated formation of sphingomyelin from erythro-cetamidts. Brain tissues have been found to inhibit the menadione-stimulated formation of sphingomyelin catalyzed by chicken liver mitochondria. Other properties of brain phosphorylcholine–ceramide transferase are also described.