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In Vitro Acetylcholinesterase Inhibition by Type A Botulinum Toxin

¹ Department of Bacteriology, Iowa State University, Ames, Iowa 50010

ABSTRACT

Type A botulinum toxin was studied for its ability to inhibit the action of acetyl-cholinesterase. The chromogenic substrate, indophenyl acetate, was used for assay of enzyme activity. Inhibition of enzyme function was detected through use of both 6.6 x 10^–6 mg (20 LD₅₀) and 6.6 x 10^–10 mg (2 x 10^–3LD₅₀) of type A botulinal toxin. Control assays were performed by use of both homologous antitoxin and heterologous antitoxins (types B and E). Enzyme inhibition was effectively prevented by use of homologous antitoxin only. The inhibition noted was specific and reproducible for given substrate, enzyme, and toxin concentrations.