Fatty Acid Amides of Ethanolamine in Mammalian Tissues.

While investigating the metabolism of ethanolamine by rat liver microsomes, we observed an incorporation of this amine into microsomal lipid that was dependent on the presence of a fatty acid as cosubstrate (1). It was shown that the product of the enzymatic reaction was the fatty acid amide of ethanolamine and that the reaction was synthetic, since little hydrolysis of added fatty acid amide could be detected. The reaction was shown to involve the direct formation of the amide and not the rearrangement of an ester. Kuehl et al. (2) had previously reported the isolation of palmitoylethanolamide, as a naturally occurring anti-inflammatory agent, from egg yolks. Since palmitoylethanolamide was known to occur in nature and to have pharmacological activity, and since there existed an enzymatic mechanism in mammalian tissues for the synthesis of this amide, we looked for the occurrence of this new lipid in mammalian tissues. The isolation, characterization, and quantitative assay of fatty acid amides of ethanolamine from animal tissues are the basis of this report.