Functional analysis of mutations in expressed acetylcholinesterase that result in azinphosmethyl and carbofuran resistance in Colorado potato beetle

The functional attributes of specific point mutations, R30K, S291G, and I392T, associated with full-length acetylcholinesterase (AChE) cDNAs of organophosphate (OP)- and carbamate-resistant Colorado potato beetles (CPB), were determined using site-directed mutagenesis and baculovirus expression. Enzymatic and inhibitory properties of altered recombinant acetylcholinesterases (rAChEs) were examined. S291G increased the hydrolysis of substrates with larger substituted alkyl groups (e.g., BTC vs ATC) and increased the inhibitory action of inhibitors with larger alkyl groups (e.g., paraoxon, DFP, and N-propyl carbofuran vs. azinphosmethyl-oxon and N-methyl carbofuran). R30K in conjunction with S291G enhanced the hydrolysis activity of larger substrates and the inhibitory action of larger inhibitors. I392T attenuated the effects of S291G in that the altered rAChE with both S291G and I392T elicited substrate specificity and inhibitory properties more similar to the susceptible form of AChE without mutations.