Acetylcholinesterase converts Met5-enkephalin-containing peptides to Met5-enkephalin.

Acetylcholinesterase (AChE; E.C. 3.1.1.7) was incubated with a number of enkephalin-containing neuropeptides found in the bovine adrenal medulla. Met5-enkephalin and Leu5-enkephalin were the most stable of the peptides studied, while precursors of Met5-enkephalin were converted to Met5-enkephalin. AChE is therefore capable of limited peptidase activity on Met5-enkephalin precursors. The enzyme hydrolysed the Met5-enkephalin precursor BAM-12P on the C-terminal side of the pair of basic amino acid residues, and cleaved basic amino acids from the carboxy-terminal of Met5-enkephalin-Arg6 and Met5-enkephalin-Arg6-Arg7. These results indicate that AChE, acting alone, is capable of the same pattern of enkephalin processing as that observed in the adrenal medulla.