Cobra Venom Acetylcholinesterase

Abstract

Acetylcholinesterase from cobra (Naja naja oxiana) venom has been purified by affinity chromatography to an homogeneous state, as ascertained by sodium dodecylsulfate/polyacrylamide gel electrophoresis and sedimentation analysis. The specific activity of the preparation was 5000 IU/mg with acetylcholine as substrate. Unlike acetylcholinesterases from insoluble cell structures, the native molecule of the cobra venom enzyme consists of a single polypeptide chain of molecular weight 67000 ± 2000. At high enzyme concentrations (> 0.2 mg/ml, > 1 μM) and ionic strength 0.1 M, it reversibly tends to form higher‐molecular‐weight 7.1‐S aggregates. Despite the apparent structural simplicity of the venom acetylcholinesterase, the disc electrophoresis and isoelectric focusing experiments revealed that the enzyme exists in a number of forms with a common molecular weight but with different isoelectric points. Neuraminidase treatment did not reduce the number of the forms.

Acetylcholinesterase from Bungarus venom: a monomeric species

“…that, in addition to glycosylation heterogeneity, charge isoforms may reflect variations in free glutamic or aspartic acids, produced by post-translational deamidation of glutamines and asparagines [15]. Such a modification may also contribute to the heterogeneity of Bungarus venom ACHE, and would explain the fact that neuraminidase treatment did not produce a single electrophoretic band.…”

Anionic subsites of the catalytic center of acetylcholinesterase from Torpedo and from cobra venom.

“…Cobra venom AcChoEase was prepared from Naja naja oxiana venom (Tashkent Integrated Zoo Plant, U.S.S.R.) by affinity chromatography as described (31 [3H]DPA was added directly from the stock solution so that the final ethanol concentration was below 5%. The sample was adjusted to 1 mM DPA with nontritiated compound.…”

Cobra Venom Acetylcholinesterase: Nature of Charge Isoforms

“…Acetylcholinesterase was purified by affinity chromatography as described elsewhere [4]. Ampholine carrier ampholytes were obtained from LKB Produkter AB (Bromma).…”

“…In the previous paper of this series it was shown that the charge differences in cobra venom acetylcholinesterase could not be attributed to different sialic acid contents in the glucosidic part of the molecule, because neuraminidase treatment did not reduce the heterogeneity of the preparation [4]. Conformational variability and multimerization were also left out since the forms appeared in the presence of high concentrations of urea [4].…”

“…Conformational variability and multimerization were also left out since the forms appeared in the presence of high concentrations of urea [4]. Consequently, charge alterations in the cobra venom acetylcholinesterase could be in the polypeptide chain of the enzyme molecule.…”