Ether lipids and platelet-activating factor: evolution and cellular function.

This review considers the relation between the evolution of ether lipids and platelet-activating factor (PAF) in living organisms for the first time. Ether lipids are shown to be the main structural lipid components in the cells of the most primitive organisms on the Earth; during evolution they were gradually substituted for lipids with ester and vinyl bonds. Synthesis of PAF has been found in some bacteria, protozoans, yeasts, plants, marine invertebrates, lower vertebrates, and mammals. The regulatory role of PAF is suggested to already appear in protozoans and later be maintained during the subsequent evolution of living organisms. During evolution, functions of PAF in the cell have been changing and enlarging, while ether lipids have been gradually losing their role as the main structural lipid component of the cells of living organisms.