Influence of ions and chelating agents on the haemolymphacetylcholinesterase of Mytilus edulis.

By use of different inhibitors as well as atomic absorption spectrophotometry it has been shown that the haemolymph-acetylcholinesterase (E. c. 3.1.1.7) of the sea mussel Mytilus edulis is a metalloprotein containing 2,95 Fe2+-ions per subunit. All inhibitors used (1,10-phenanthroline, salicylic aldehyde, 2,2'-dipyridyl, 8-hydroxyquinoline) showed a non-competitive inhibition, which was not pH-dependent. Some divalent cations caused a marked increase of the enzyme activity, some heavy metals inhibited the enzyme almost completely; monovalent inorganic cations did not influence the enzyme at all. Besides NaF and Na2SiF6, which showed a non-competitive inhibition comparable to the inhibition observed with the chelating agents, and NaN3, whose mode of action was not identifiable, no inhibition by different mono- and divalent inorganic anions was to be observed. Ammonium ions caused no enzyme inhibition, but length the inhibition power of substituted ammonium ions increased with an increasing C-chain. The influence of some organic solvents on the enzyme activity is demonstrated.