Selective activity of butyrylcholinesterase in serum by a chemiluminescentassay

In a previous study, we showed that purified commercial esterase activity c an be detected in a chemiluminescent assay based on the hydrolysis of 2-met hyl-1-propenylbenzoate (MPB) to 2-methyl-1-propenol, which is subsequently oxidized by the horseradish peroxidase (HRP)-H2O2 system. The purpose of th is study was to verify the applicability of this assay to human serum. The existence of an esterase activity capable of hydrolysing MPB is indicated b y the fact that the MPB-scruin-HRP-H2O2 System consumes oxygen and emits li ght. Both signals were abolished by prior serum heat inactivation and were preserved when serum was stored at less than or equal to4 degreesC. Additio n of aliesterase inhibitors, such as fluoride ion and trichlorfon or the ch olinesterase inhibitor eserine, totally prevents light emission. The butyry lcholinesterase-specific substrate benzoylcholine causes a delay in both O- 2 uptake and light emission, while the specific acetylcholinesterase substr ate, acetyl-beta -methylcholine, had practically no effect. Purified butyry lcholinesterase, but not acetylcholinesterase, triggered light emission. Th e finding that butyryleholinesterase is responsible for the hydrolysis of M PB in serum should serve as the basis for the development of a specific che miluminescent assay for this enzyme. Copyright (C) 2001 John Wiley & Sons, Ltd.