Enzymatic synthesis and decarboxylation of phosphatidylserine in Tetrahymena pyriformis

Cell-free extracts of the protozoan Tetrahymena pyriformis have been found to catalyze the following reactions: Phosphatidylethanolamine+L-Serine⇌Phosphatidylserine+EthanolaminePhosphatidylserine→Phosphatidylethanolamine+CO2Net:L-Serine→Ethanolamine+CO2The biosynthesis of phosphatidylserine in this organism resembles that found in higher animals. In contrast, phosphatidylserine is formed in bacteria in a reaction between CDP-diglyceride and l-serine. A detailed description is presented of the enzyme that catalyzes the synthesis of phosphatidylserine in Tetrahymena by the exchange reaction, together with some properties of the phosphatidylserine decarboxylase in this organism.