ACETYLCHOLINESTERASE IN APIS-MELLIFERA HEAD DURING POSTEMBRYONIC DEVELOPMENT - EXISTENCE OF A GLYCOINOSITOL-ANCHORED MEMBRANE FORM AT EARLY PUPAL STAGES

1. Properties of acetylcholinesterase (AChE, EC 3.1.1.7) from Apis mellifera head were studied during pupal development and at the adult stage. 2. During post-embryonic development, tissue and specific activities were closely related and increased to reach a maximum value at emergence and at last pupal stage, respectively. 3. In adults, AChE activity was weaker in foragers than in emerging bees. 4. The membrane form occurred in adult bees as well as in pupae whereas the soluble enzyme only appeared from Pd pupal stage. 5. The proportion of soluble and membrane forms fluctuated during late development but, in all cases, the percentage of the soluble form remained less than 10% of total AChE activity. 6. At all post-embryonic stages, the membrane form was sensitive to the action of phosphatidylinositol-specific phospholipase C (PI-PLC) and was converted into a hydrophilic enzyme. 7. In adult bees, the sensitivity to PI-PLC depended on the season. In summer, about 60% of the membrane activity could be solubilized by PI-PLC vs only 5% in winter. 8. The sensitivity of AChE to pirimicarb varied with the developmental (sic). 9. In foraging bees, AChE was more susceptible to pirimicarb than in (sic) bees. This difference of sensitivity to carbamate was abolished after removal of the membrane anchor either by mild trypsin digestion or PI-PLC treatment.