Immunoenzymology of acetylcholinesterase—III

Venom exonuclease. III. Immunochemical characterization and modification by specific antibody

The immunoelectrophoretic purity of the exonuclease preparation, isolated from Crotalus adamanteus venom according to a procedure previously published (Dolapchiev, L.B., Sulkowski, E. and Laskowski, M., Sr. (1974) Biochem. Biophys. Res. Commun. 61, 271-281), is reported. The enzyme showed one precipitin line against antibody prepared against partially purified venom. The exonuclease is unstable in dilute (1.25 microgram/ml and below) solutions. Bovine serum albumin stabilized the enzyme nonspecifically whereas the homologous antibody demonstrated a specific stabilizing effect under the same conditions. The binding of the anti-enzyme with the enzyme caused inhibition of both its activities--phosphodiesterase and pyrophosphatase. The inhibition of the exonuclease when attacking high molecular weight substrates is similar to the above and is of the same noncompetitive type. The thermal stability of venom exonuclease is reported.

Torpedo marmorata acetylcholinesterase; a comparison with the Electrophorus electricus enzyme. Molecular forms, subunits, electron microscopy, immunological relationship

Electron microscopy, sequential degradation by hydrolytic enzymes and the physical-chemical properties of the molecular forms of Torpedo acetylcholinesterase indicate that these molecules are structurally related to each other in the same way as the molecular forms of Electrophorus acetylcholinesterase: all are derived from a complex structure in which three tetrameric groups of subunits are associated with a rod-like 'tail'. In aged preparations the catalytic subunits are split into fragments in a manner similar to those of Electrophorus acetylcholinesterase. Immunological cross-reaction between both enzymes demonstrates the occurrence of common antigenic sites. The enzymes from the two sources, however, are different in their molecular weights and susceptibility to hydrolytic enzymes. Also, Torpedo acetylcholinesterase does not precipitate with either isologous or heterologous antibodies.