M. Sanders et al., BIOCHEMICAL AND MOLECULAR CHARACTERIZATION OF ACETYLCHOLINESTERASE FROM THE HAGFISH MYXINE GLUTINOSA, Comparative biochemistry and physiology. B. Comparative biochemistry, 115(1), 1996, pp. 97-109
To obtain information about the evolution of the cholinesterases, we i
nvestigated the cholinesterase activity of an agnathan vertebrate, the
hagfish Myxine glutinosa. On the basis of evidence from enzymology, p
harmacology, and molecular biology, we conclude that the cholinesteras
e activity is due to acetylcholinesterase (AChE). The enzyme hydrolyze
s acetylthiocholine preferentially and exhibits substrate inhibition.
The hydrolysis of both acetylthiocholine and butyrylthiocholine are in
hibited in parallel by cholinesterase inhibitors, with the AChE-specif
ic drug BW284c51 being the most potent; however, this drug and propidi
um, a peripheral anionic site ligand, are much weaker inhibitors of th
e hagfish enzyme than of Torpedo AChE. We used sequential extraction,
collagenase digestion, and velocity sedimentation on sucrose gradients
to determine that the AChE from the skeletal muscle of the hagfish is
present in both globular and asymmetric forms. We also used the polym
erase chain reaction with degenerate oligonucleotide probes and genomi
c DNA to obtain a 1 kb gene fragment for hagfish AChE. The enzyme has
an acyl binding site typical of other vertebrate AChE, but lacks two a
romatic residues implicated in the function of the peripheral anionic
subsite. We discuss the relevance of our findings to the evolution of
the cholinesterases in the vertebrates.