Activity, localization and molecular form of acetylcholinesterase in the male accessory glands of metamorphosing Tenebrio molitor L.

Abstract

Despite their mesodermal origin, male accessory glands of the reproductive system of Tenebrio molitor exhibited marked acetylcholinesterase (AChE) activity throughout metamorphosis (i.e. from the newly ecdysed pupa to the mature adult stages). This activity was true AChE activity, since it was inhibited by high concentrations of substrate and by 10 −5 M BW284C51 dibromide, but not by iso-OMPA. The AChE activity was exclusively localized in the muscular coat of the glands and not in the epithelial cells which secreted the spermatophore proteins. The enzyme extracted from the glands with 1% Triton X-100 and 1 M NaCl sedimented as a single peak in a sucrose density gradient, with a sedimentation coefficient of 5.4 S. This single AChE sedimentation peak was not altered after treatment with DTT or β-mercaptoethanol. AChE activity per gland increased throughout metamorphosis. Activity per mg of wet weight of glands rose at the mid pupal stage. It decreased at adult ecdysis to the level of the newly edysed pupa. AChE activity per mg of protein exhibited a peak in the young pupa.