Cobra venom acetylcholinesterase: nature of charge isoforms.

Charge isoforms of cobra (Naja naja oxiana) venom acetylcholinesterase, separated by isoelectric focusing, differ only by the number of free carboxyl groups of glutamic and/or aspartic acid side-chains in the enzyme molecule. The isoforms appear to be produced by a post-translational deamidation of accessible glutamin and/or asparagine residues. The isoforms have identical catalytic specificities towards characteristic acetylcholinesterase substrates.