ABSTRACT
This chapter discusses the role of phospholipid metabolism in important physiological processes as well as some aspects of its regulation. Other phospholipid-specific hydrolases, such as the phospholipases C and D, responsible for the hydrolytic removal of the phosphocholine and the choline group of phosphatidylcholine, respectively, were shown to exist in bacteria and plants but went for a very long time unnoticed in cells of animal origin. The other enzyme possibly specific to phosphatidylethanolamine biosynthesis is ethanolamine kinase. There has been considerable debate in the literature about the existence of two different kinases for choline and ethanolamine. In line with the distinctly different properties of the ethanolamine- and the choline-phosphate cytidylyltransferases, the regulation of phosphatidylethanolamine biosynthesis, although considerably less well investigated than that of phosphatidylcholine synthesis, differs significantly from the latter. A substantial proportion of the phosphatidylcholine and phosphatidylethanolamine fraction of cells, particularly in electrically active organs and tissues, belongs to the so-called ether phospholipids.
