How do I screen for acetylcholinesterase activity?

Acetylcholinesterase (AChE) is a key enzyme responsible for terminating neuronal transmission and signaling. The most common method for screening AChE activity is to use the Ellman’s method. This assay is based on the hydrolysis of the substrate acetylthiocholine by AChE to yield the product thiocholine. Thiocholine is then reacted with Ellman’s reagent (5,5'-dithio-bis-(2-nitrobenzoic acid) or DTNB) resulting in a yellow-colored product that can be quantified using a spectrophotometer at 412 nm. The rate of color formation is directly proportional to the activity of AChE.