[The cholinesterase properties of Daphnia magna].

It has been demonstrated that cholinesterase of Daphnia magna is capable of the hydrolysis of propionylthiocholine iodide at the highest rate as compared to the other substrates studied, the hydrolysis being inhibited by high concentrations of the substrate. The rate of splitting of acetylthiocholine iodide is similar to that of propionylthiocholine iodide, whereas the hydrolysis of butyrylthiocholine iodide is 3 times slower. Cholinesterase from D. magna is extremely sensitive to an organophosphorus inhibitor, DDVP. The value of bimolecular constant of the inhibition rate (kappa II) is equal to (1.60 +/- 0.20).10(8)1.mol-1.min-1.