Acetylcholinesterase is an Old biomarker or New biomarker

Abstract

Cholinesterases (ChEs) activity in fish brain was used fairly widely during the 1960’s and 1970’s as a “biomarker” to assess the scale of impact during large scale pesticide spraying operations, but its use declined somewhat during the 1980’s, perhaps as analytical chemistry methods for organophosphates and carbamates became more accessible. During the 1990’s there was a resurgence of interest in the use of ChE as a “biomarker” as evidence accumulated that ChE activity in fish was inhibited at sites not obviously contaminated by organophosphate or carbamate pesticides and although the chemical cause of such inhibition is still unidentified, ChE is being used as a bioassay to identify potentially contaminated sites which can be examined in more detail using the approaches of analytical chemistry.ChE in marbled sole were characterized; in brain, ChE existed almost exclusively (95%) of acetylcholinesterase (AChE) whereas in muscle, about 20% of ChE activity was in the form of butyrylcholinesterase (BChE; pseudocholinesterase). Brain AChE and muscle AChE and BChE were characterized in terms of their kinetic properties (KM etc.) and optimal conditions (substrate concentration, protein concentration, pH etc.) were established to allow routine assays of ChE activity to proceed under pseudo-first order conditions. The sensitivity of ChEs to a locally-significant pesticide, iprobenfos (IBP) was established in terms of IC50 concentrations; brain AChE was relatively insensitive to IBP, but muscle AChE and BChE were sensitive to IBP concentrations in the low μM range. Therefore, ChE assay is a valuable tool to confirm chemicals that are known to exert potential biological damage.