[Biosynthesis and metabolism of phosphonolipids and phospholipids in rat hepatocytes and Saccharomyces cerevisiae].

In rat hepatocytes, ciliatine (2 aminoéthylphosphonic acid) is incorporated into phosphonolipid (PnE) by the same pathway leading from phosphorylethanolamine to phospholipid (PE). The two resulting lipids are isolated from mitochondria and microsomes. The rates of biosynthesis are quite comparable; the processes of trimethylation and of in vitro transfer in the presence of a specific exchange protein are very similar. In yeast, on the other hand, the uptake of the two precursors is very slight, suggesting that the direct cytidylic pathway of phospholipid biosynthesis is strongly repressed. Despite small amounts of PE and PnE produced, methylation occurs with a good yield. The good incorporation of ethanolamine may be understood by a base-exchange mechanism. The natural PE biosynthesis is achieved through the decarboxylation of phosphatidylserine, and followed by methylation leading to phosphatidylcholine. The use of very small amounts of precursors does not modify the natural course of phospholipid biosynthesis.