Acetylcholinesterase of Schistosoma mansoni: Molecular forms of the solubilized enzyme

Abstract

Several molecular forms of acetylcholinesterase were obtained from Schistosoma mansoni homogenates by extraction in either low-salt buffer, high-salt buffer or detergent buffer. The low-salt soluble form amounts to 25% of the total activity. By constant, the extract obtained in the presence of Triton X-100 possessed almost 3-fold higher enzymatid activity, most of it (86%) being retained in the soluble extract (100 000 × g). High-salt concentration (1 M NaCl) also has a solubizing effect, but to a lesser extent (50%). Acetylcholinesterase can also be solubilized by treatment with a solution of 1% methylmannoside (40%). In the presence of non-ionic detergents, the enzyme behaves as monodisperse 8 S form. In the absence of detergent the low-salt soluble extract is polydisperse: it contains a 10 S and a 32 S component, the latter could represent high polymers. The molecular form released from tissue homogenate by treatment with α-methylmannoside is polydisperse: it contains a major 10 S and a minor 32 S component. Differences in sedimentation coefficient were observed among the enzymes extracted with detergent from the various life cycle stages of the parasite. The enzyme from the cercarial stage sediments as a single 8 S peak. The adult worm exhibits an additional acetylcholinesterase peak of 18 S representing approx. 30% of the total enzymatic activity. The molecular weight of the major 8 S species, as determined by gel filtration, is 450 000.