Determination and characterization of cholinesterases in localized tissues of the giant garden slugs Limax maximus (Linnaeus)

1. Evidence is presented for the presence of two types of cholinesterase in localized tissues of the terrestrial slug, Limax maximus, by use of substrates, inhibitors, and differential centrifugation. 2. An acetylcholine-type enzyme (AChE, EC 3.1.1.7) occurs in the circumoesophageal ganglia and muscular foot of the animal. It exhibits novel properties, including appreciable activity towards propionyl esters, lower sensitivity to inhibition by the AChE inhibitor BW284C51, and passes spontaneously (> 99%) into solution. 3. A second enzyme occurs in the hemolymph. It exhibits a substrate-activity profile characteristic of a non-specific propionylcholinesterase (PrChE, EC 3.1.1.8). 4. PrChE in Limax hemolymph (about 50% of the total activity) is associated with material pelletable in a 110,000 g spin presumed to be hemocyanin. 5. Progressive inhibition with iso-OMPA reveals that each enzyme is composed of two components. The AChE-type enzyme has a component, comprising 35% of the total activity, that is highly resistant to iso-OMPA inhibition. A similarly resistant component is absent in the hemolymph enzyme.