Arachidonoyl p-nitroaniline is a substrate for the hydrolysis of p-nitroaniline by FAAH in Dictyostelium discoideum with long-chain unsaturated fatty acids. Arachidonoyl p-nitroaniline can be used in enzyme kinetic studies. Examples include determining the hydrolysis rate of Arachidonoyl p-nitroaniline and analyzing the fatty acid amide hydrolase activity of recombinant His-FAAH purified from Dictyostelium to characterize the binding and catalytic specificity of mammalian FAAH enzymes^[1].