The application of mass spectrometry to elucidate the biosynthesis of long-chain fatty acid amides

L fatty acid amides are a family of endogenous signaling lipids that have various biological functions in mammals. The general structure of a fatty acid amide is R-CO-NH-X, where R is an acyl group and X is derived from a vast variety of biogenic amines; members of this family include the N-acylethanolamines, N-acylamino acids, the N-acylarylalkylamides, the N-monoacylpolyamides, and the primary fatty acid amides. These metabolites are lowly abundant in biological samples and are often difficult to identify and quantify. We employed LC/QTOF-MS analysis to study long-chain fatty acid amide metabolism in two model systems, mouse N18TG2 neuroblastoma cells and Drosophila melanogaster. The best studied long-chain fatty acid amide is the mammalian endocannabinoid, N-arachidonoylethanolamine (anandamide). However, many of the details of non-N-acylethanolamine long-chain fatty acid amide metabolism are not known in mammals or invertebrates. Full details of long-chain fatty acid amide metabolism will lead to the discovery of invaluable therapeutic targets. Herein, heavy-labeled precursor studies and siRNA mediated subtraction lipidomic analysis utilizing LC/QTOF-MS technology led to the elucidation of the enzyme responsible for N-acylglycine biosynthesis.