An acetylcholinesterase was purified from the gut of sea cucumber Stichopus japonicus by anion exchange chromatography followed by gel filtration chromatography. The enzyme was purified 35. 49-fold with a total yield of 7. 73 %. The molecular mass of purified acetylcholinesterase was 68 kDa as revealed on sodium dodecyl sulfate polyacrylamide gel electrophoresis. The enzyme displayed maximum activity at pH 7. 5 and 35 °C with acetylthiocholine iodide as substrate. The enzyme activity appeared to be stable over pH 6. 0-8. 0 and up to 40 °C. It displayed an apparent Michaelis-Menten behavior in the concentration range from 0. 1 to 0. 8 mM with Km values of 0. 62 mM for acetylthiocholine iodide and 2. 53 mM for butyrylthiocholine iodide. More than 95 % of acetylcholinesterase activity was inhibited by 1 mM eserine or 1,5-bis(4-allyldimethylammonium phenyl)-pentan-3-one dibromide (BW284C51), but only 19. 1 % of the activity was inhibited by tetraisopropylpyrophosphoramide (iso-OMPA) at the same concentration. On the basis of the substrate and inhibitor specificities, the purified enzyme appeared to be a true acetylcholinesterase. Nevertheless, the purified acetylcholinesterase exhibited insensitivity to substrate inhibition phenomenon. Its biochemical properties were compared with those reported for different species.
- Sea cucumber Stichopus japonicus
ASJC Scopus subject areas
- Aquatic Science