A Novel Class of Acetylcholinesterase,Revealed by Mutations,in the Nematode Caenorhabditis elegans

In ace-2;ace-1 double mutants of the nematode C. elegans, where the major acetylcholinesterase (AChE) classes A and B have been eliminated by mutation, the animals are viable and residual AChE activity remains. This residual activity differs markedly from AChE classes A and B; its K_m for acetylcholine is 1000-5000-fold lower, its resistance to eserine is 3000-260,000-fold higher, it is markedly more thermo-labile, and it can be separated from classes A and B by ion exchange chromatography. It has been designated class C AChE. Class C AChE of indistinguishable properties is also present in wild type C. elegans, at levels approximating those seen in ace-2;ace-1 double mutants, suggesting that it is controlled by a third, as yet unidentified, gene. Amongst other sources examined, class C-like AChE has been detected in another nematode species, Stepkanurus dentatus, but not in Drosophila melanogaster, Torpedo californica, or Rattus rattus.