In this work we assess the potential of acetylcholinesterase (AChE) from Oreochromis
mossambicus (Toman) as a sensitive test for the presence of insecticides. The partial purification
and characterization of a soluble AChE from Oreochromis mossambicus brain tissues using
affinity chromatography gel (procainamide–Sephacryl S-1000) showed that the partially purified
AChE was most active on acetylthiocholine (ATC) but had low activities on
propionylthiocholine (PTC) and butyrylthiocholine (BTC), indicating that the partially purified
fraction was predominantly AChE. Soluble AChE was partially purified 9.27-fold with a 91.12%
yield. The partially purified AChE displayed the highest activity on ATC at pH 7 and at 30oC
using 0.1 M Tris buffer. The enzyme exhibited Michaelis-Menten kinetic constants, Km, for
ATC, BTC and PTC at 36, 77 and 250 μM, respectively, and the maximum velocities, Vmax, were
18.75, 0.12 and 0.05 μmol/min/mg protein, respectively. Moreover, the AChE from
Oreochromis mossambicus presented comparable sensitivity to carbamates and
organophosphates insecticides than that from Electrophorus electricus and many other fish
AChE by comparing half maximal inhibitory concentration values. Therefore, the enzyme is a
valuable source for insecticides detection in Malaysian waters at lower cost.