CHARACTERIZATION OF ACETYLCHOLINESTERASE PURIFIED FROM THE LESSER GRAIN BORER, RHYZOPERTHA-DOMINICA (COLEOPTERA, BOSTRICHIDAE)

1. Acetylcholinesterase (AChE, EC 3.1.1.7) purified from the lesser gr ain borer (Rhyzopertha dominica) was significantly inhibited by higher concentrations of the substrates acetylthiocholine (ATC), acetyl-(bet a-methyl) thiocholine (A beta MTC) and propionylthiocholine (PTC). 2. The efficiency of ACHE for hydrolyzing different substrates was ATC > A beta MTC > PTC > S-butyrylthiocholine. The enzyme activity was compl etely inhibited by 10(-5) M eserine or BW284C51, but was only partiall y inhibited by ethopropazine at the same concentration. These results confirmed that the purified enzyme was an typical insect ACHE. 3. Non- denaturing and SDS polyacrylamide gel electrophoresis (PAGE) showed on ly one major molecular form in the purified ACHE with a molecular weig ht of about 107,000 prior to reduction and about 56,000 after reductio n, suggesting the homodimer of ACHE linked with disulfide bonds. (C) 1 998 Elsevier Science Inc.