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Comparison of properties of native and lytic forms of acetylcholinesterase from Apis mellifera
Author(s) -
Belzunces Luc P.,
Debras JeanFrançois
Publication year - 1997
Publication title -
archives of insect biochemistry and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.576
H-Index - 66
eISSN - 1520-6327
pISSN - 0739-4462
DOI - 10.1002/(sici)1520-6327(1997)34:2<143::aid-arch2>3.0.co;2-y
Subject(s) - chemistry , stereochemistry , biochemistry
The properties of purified native soluble AChE (sAChE) from Apis mellifera were compared with those of purified membrane AChE (mAChE), mAChE solubilized with phosphatidylinositol‐specific phospholipase C (AChEPI‐PLC), glycosyl phosphatidylinositol‐specific phospholipase D (AChEGPI‐PLD) and trypsin (AChETi), and other soluble derivative forms obtained from mAChE by autolysis (AChELyt) or limited digestions with proteinase K or chymotrypsin. Analysis by non‐denaturing electrophoresis showed that the electrophoretic mobilities of all lytic soluble forms were higher than that of sAChE. sAChE had a K m value of about 90 μM whereas mAChE, AChETi, AChELyt, AChEPI‐PLC, and AChEGPI‐PLD displayed a lower K m value of about 20 μM. The sensitivity to organophosphates was lower for sAChE than for mAChE, AChETi, AChEPI‐PLC, and AChEGPI‐PLD and was due to higher K d and lower k 2 values observed for sAChE. In Arrhenius plot analysis, mAChE, AChETi, AChEPI‐PLC, and AChEGPI‐PLD displayed a homogenous behaviour whereas sAChE exhibited a highly reproducible break at 18°C. Thermal stability studies at 52°C revealed that sAChE, AChEPI‐PLC, and AChEGPI‐PLD displayed the highest thermal stability with inactivation constants of about 0.020 min −1 . This high thermal stability contrasted with those of mAChE, AChELyt, and AChETi, which exhibited respective inactivation constants of 0.051, 0.074, and 0.171 min −1 . These results suggest that sAChE is not the mere cleavage product of mAChE by endogenous (glycosyl) phosphatidylinositol‐specific phospholipase C/D or proteases. Arch. Insect Biochem. Physiol. 34:143–157, 1997. © 1997 Wiley‐Liss, Inc.