Seven cases involving acute fatalities due to ingestion of furathiocarb, a carbamate insecticide, are presented. Furathiocarb was detected in the gastric contents using thin layer chromatography (TLC) and gas chromatography/mass spectrophotometry (GC/MS), and quantified in the blood using a gas chromatograph equipped with a nitrogen-phosphorus detector (NPD). The fatal levels of furathiocarb in the blood ranged from 0.1 to 21.6 micrograms/ml.
Title: Probing the acyl binding site of acetylcholinesterase by protein engineering Pleiss J, Mionetto N, Schmid RD Ref: J Mol Catal B Enzym, 6:287, 1999 : PubMed
Recombinant acetylcholinesterase from rat brain and two mutants were studied for their hydrolytic activity toward acetyl- and butyrylthiocholine substrates and for their sensitivity toward organophosphate and carbamate inhibitors. Both mutants, a point mutant where F295 was replaced by leucine, and a second mutant where loop PQES was replaced by SG, were designed for increased size of the acyl binding pocket. Wild type and mutant enzymes were expressed in baculovirus-infected insect cells and biochemically characterized. As expected, wild type rat brain acetylcholinesterase hydrolyzed acetylthiocholine, but not butyrylthiocholine.
Sensitivity toward small- and medium-sized organophosphate inhibitors like paraoxon-methyl and paraoxon-ethyl was comparable, but bulky organophosphates like ethoprophos were less efficient inhibitors. This tendency applied to carbamates as well, since small carbamoyl moieties like carbofuran and aldicarb were stronger inhibitors than furathiocarb which features a bulky carbamoyl moiety. In contrast to wild type enzyme, both mutants were capable of hydrolyzing butyrylthiocholine. However, kcat/Km toward acetylthiocholine of the F295L mutant was reduced if compared to the wild type enzyme.
All five organophosphate and three carbamate inhibitors inhibited mutant F295L
more efficiently than the wild type enzyme.
