ACETYLCHOLINESTERASE FROM THE HORN FLY (DIPTERA, MUSCIDAE) - DISTRIBUTION AND PURIFICATION

Acetylcholinesterase (AChE) in newly emerged adults of the horn fly, Haematobia irritans (L.), was distributed mostly in the head (72.9%), less in the thorax (24.4%), and least in the abdomen (2.7%). The major portion of total AChE was membrane-bound and associated primarily with the microsomes. The enzyme was solubilized with phosphate buffer containing 0.5% (vol/vol) of Triton X-100 and purified with affinity chromatography. The extent of purification was about 217-fold for the membranous fraction and 329-fold for the soluble fraction of whole fly homogenates with recoveries of 55% and 79%, respectively. The extent of purification reached 600- and 784-fold for the membranous and the soluble fractions, respectively, in the collections of eluents with peaked activity of AChE. Electrophoresis revealed four bands of AChE activity in the membrane-bound preparation and three bands in the soluble preparation. Silver staining of the electrophoresed gels showed that the major proteins in purified AChE solutions corresponded with AChE bands.