Immunoassay of acetylcholinesterase

There is a twofold rationale for assaying acetylcholinesterase (AChE) (EC 3.1.1.7) immunologically, rather than by conventional activity-based methods: to measure the amount of enzyme protein in samples that may contain AChE of uncertain intrinsic activity; to bypass cumbersome procedures for determining the individual molecular forms of the enzyme. We have developed an immunodisplacement assay and a two-site immunoassay for AChE that are sensitive enough to measure the enzyme in samples of biological interest (assay thresholds of 10 and 0.1 ng, respectively). We have also used immunofluorescence with quantitative cell sorting as a means of analyzing AChE immunoreactivity in normal and abnormal human red blood cells. The introduction of form-specific immunoassays awaits the identification of suitably selective antibodies.