Differential behaviour of eel and erythrocyte acetylcholinesterase on N-methylacridine affinity columns. Importance of ligand affinity and concentration

The retention and elution of acetylcholinesterase from bovine erythrocytes and electric eel on N-methylacridinium affinity columns have been compared at various ligand concentrations. A soluble 7.7 S dimeric form of bovine erythrocyte acetylcholinesterase required a ligand concentration of 2.0-2.8 mumol/ml in 0.1 M NaCl for retention, compared to 0.44 mumol/ml for various forms of the electric eel acetylcholinesterase. The difference in the retention of acetylcholinesterase from these two sources could not be explained by differences in their oligomeric structure. The affinity of bovine erythrocyte acetylcholinesterase for N-methylacridinium was 13-fold or more lower than the electric eel acetylcholinesterase at similar ionic strengths. N-Methylacridinium appeared to react selectively with the catalytic anionic site of both enzymes. It was concluded that the affinity of the side arm ligand was the major determinant of the differences in the retention properties of the eel and erythrocyte acetylcholinesterase. The difference in affinity for N-methylacridinium probably reflects differences in the organic cation binding region of the two enzymes.

Acetylcholinesterase: characterization of native and proteolytically derived forms and identification of structural protein components

The assymmetric 18S and 14S forms of acetylcholinesterase (EC 3.1.1.7) from Electrophorus electricus purified by affinity chromatography on N-methylacridinium Sepharose 2B were subjected to trypsin or collagenase proteolysis and changes in the enzyme composition and structure were monitored by sucrose gradient sedimentation, gel chromatography, and sodium dodecyl sulphate - polyacrylamide gel electrophoresis. A distinction between autolytic and tryptic degradation products is described and the generation of two new forms of acetylcholinesterase from the 18S and 14S enzyme by collagenase proteolysis is reported. The species derived from the 18S form of acetylcholinesterase has a sedimentation coefficient of 21.1S and a Stokes radius of 12.9 nm while the 14S form gives rise to a 17.3S species with a Stokes radius of 11.1 nm. The proteolytically sensitive component ('tail') of the asymmetric forms of acetylcholinesterase is identified with a subunit of 45 000 daltons on sodium dodecyl sulphate - polyacrylamide electrophoresis gels.

Partial purification and some properties of a cholinesterase from bush bean (Phaseolus vulgaris L.) roots

A cholinesterase was partially purified from bush bean (Phaseolus vulgaris L.) roots by using acridinium-based ligand affinity chromatography. The procedure gave a 78-fold increase in specific activity, although at least three inactive contaminants remained. The enzyme activity was maximal against acetyl esters of choline and was inhibited by neostigmine. Di-isopropyl phosphorofluoridate completely inhibited activity at concentrations greater than 0.1 mM. The catalytic centre activity was 2 X 10(-4) times that of electric eel acetylcholinesterase. Cholinesterase activity appeared as a peak (s = 4.2 +/- 0.1 S) after isokinetic sedimentation. The Stokes radius was 4.00 nm and the apparent molecular weight was 72700 +/- 1900. The smallest active and native form of the enzyme appeared to be a monomer. This contrasts with animal acetylcholinesterases, in which the smallest active and native forms are multimeric.

Subxiphoid pericardial window in patients with suspected traumatic pericardial tamponade

The technique, indications, and results of subxiphoid pericardial window in penetrating chest wounds with suspected traumatic pericardial tamponade are reported. The classic signs of pericardial tamponade (elevated central venous pressure, muffled heart sounds, and paradoxical pulse) are unreliable in an emergency situation. Chest roentgenograms and electrocardiograms are of little diagnostic value. Pericardicentesis was either falsely positive or negative in 50% of our patients. Therefore, unexplained high central venous pressure and hypotension were considered to be pericardial tamponade until disproved by the results of a subxiphoid pericardial window. There were 4 negative and 46 positive findings of tamponade in 50 consecutive patients with suspected traumatic pericardial tamponade who underwent creation of a subxiphoid pericardial window. There were no deaths or complications from the procedures. The early use of subxiphoid pericardial window has been a major factor in reducing our mortality rate from penetrating heart wounds to 12% overall, and 8% in the past three years.