Molecular characterization of Hydra acetylcholinesterase and its catalytic activity.

A full-length cDNA encoding an acetylcholinesterase (AChE) from Hydra magnipapillata was isolated. All of the important aromatic residues that line a catalytic gorge in cholinesterases of other species were conserved, but the sequences of peripheral anionic and choline binding sites were not. Hydra AChE, expressed in Xenopus oocytes, showed AChE activity. The gene was expressed in both ectodermal and endodermal epithelial cells except for the tentacles and basal disk. AChE gene expression was not detected in the regenerating tips in either the head or the foot, indicating that regeneration is controlled by the non-neuronal cholinergic system in Hydra.