THE PROPORTION OF AMPHIPHILIC CHOLINE-ACETYLTRANSFERASE IN DROSOPHILA-MELANOGASTER IS HIGHER THAN IN RAT OR TORPEDO AND IS DEVELOPMENTALLY REGULATED

We show that in the central nervous system of the fly, Drosophila mela nogaster, choline acetyltransferase (ChAT) activity exists under two m olecular forms, a soluble, hydrophilic form and a membrane-bound, amph iphilic form. This is based on the following demonstrations of differe ntial solubilization and interaction with non-denaturing detergents: s equential extraction of Drosophila heads produced low-salt-soluble (83 -87%) and detergent-soluble (6-7%) ChAT activity. Sedimentation in suc rose gradients of detergent-soluble ChAT was found to be influenced by the type of detergent present in the gradient (Triton X-100 and Brij %). This was not the case for low-salt-soluble ChAT. To further confir m these findings, we subjected Drosophila heads to Triton X-114 fracti onation. This method, which yielded 12% of amphiphilic ChAT activity, separates hydrophilic from amphiphilic proteins. Compared to central n ervous tissue of rat and Torpedo electric lobes, Drosophila head conta ined the highest proportion of amphiphilic ChAT activity. Synaptosomes isolated from Torpedo electric organ exhibited higher levels of amphi philic ChAT than did electric lobes. Of the three animal species analy zed here, the Torpedo amphiphilic enzyme was the most hydrophobic and the rat enzyme the least hydrophobic. The proportion of amphiphilic Ch AT was analyzed during Drosophila development. The percentage of this activity increased about 7 times from embryo to larva and then remaine d constant until the adult fly age.