ApNA is one of several nitroaniline fatty acid amides which can be used to measure FAAH activity. FAAH is a relatively unselective enzyme in that it accepts a variety of amide head groups other than the ethanolamine of its nominal endogenous substrate AEA (Item No. 90050). It also will hydrolyze fatty acid amides with fewer carbons and fewer double bonds than arachidonate. (See also Decanoyl p-Nitroaniline - Catalog No. 90349). Exposure of ApNA to FAAH activity results in the release of the yellow colorimetric dye p-nitroaniline (ε = 13,500 at 382 nm). This offers the potential for fast and convenient measurements of FAAH activity using a 96-well plate spectrophotometer.