Tetraalkylammonium (TAA) salts are well known reversible inhibitors of cholinesterases. However, at concentrations around 10 mM, they have been found to activate the hydrolysis of positively charged substrates, catalyzed by wild-type human butyrylcholinesterase (EC ) [Erdoes, ., Foldes, ., Zsigmond, ., Baart, N. & Zwartz, . (1958) Science 128, 92].