Partial characterization of phosphotriesterase activity from the earthworm, Eisenia andrei

Phosphotriesterase (PTE) receives attention because it seems to be associat ed with the detoxification of organophosphorous pesticides and organophosph ate resistance mechanism. In order to understand the biodegradation of phos photriester pesticides and its significance in the earthworm, a major non-t arget animal of pesticides, selected properties of phosphotriesterase activ ity derived from the crude extract of Eisenia andrei were investigated. PTE activity appeared to be primarily localized in intestinal tissues. The hig hest level of PTE activity was found in epithelial tissue. The native molec ular weight of earthworm PTE was 260 kDa and the isoelectric point was appr oximately 4. The optimal pH was approximately 9. The earthworm PTE had a su bstrate affinity for paraoxon with K-m value in the millimolar range. The p resence of EGTA and EDTA completely abolished the activity and replacement of Ca2+ ion restored activity to greater than 95%, suggesting that Ca2+ ion is essential to maintain the activity. (C) 2001 Elsevier Science Ltd. All rights reserved.