Anatoxin-a(s), an anticholinesterase from the cyanobacterium Anabaena flos-aquae NRC-525-17

Abstract

N. A. Mahmood and W. W. Carmichael. Anatoxin-a(s), an anticholinesterase from the cyanobacterium Anabaena flos-aquae NRC-525-17. Toxicon 25, 1221 – 1227, 1987. — Anatoxin-a(s) [antx-a(s)] given intraperitoneally to Sprague-Dawley rats at different doses (0.1 – 1.0 mg/kg) caused signs of severe cholinergic overstimulation. Assays of rat blood acetylcholinesterase (AChE) revealed a dose-dependent inhibition. The in vitro inhibition of electric eel acetylcholinesterase (AChE, E.C. 3.1.1.7) and horse serum butyrylcholinesterase (BUChE, E.C. 3.1.1.8) by antx-a(s) was time- and concentration-dependent. The inhibition of electric eel AChE follows first order kinetics, indicative of irreversible inhibition. The irreversibility of electric eel AChE inhibition was confirmed by a plot of V max versus total enzyme concentration [ E T ]. The kinetics of inhibition of cholinesterase by antx-a(s) supports the previous pharmacological findings that antx-a(s) is an anticholinesterase and that signs of intoxication by it are primarily due to cholinesterase inhibition.