Enzymatic hydrolysis and reversible binding of suberyldicholine by cholinesterases

A hydrolysis of suberyldicholine and monocholic ester of suberic acid by butyrylcholinesterase was studied. In the region of Sopt the rates of suberyldicholine hydrolysis were slightly below and under S less than Sopt they were far in excess of the rates of acetylcholine hydrolysis. The following kinetic constants of hydrolysis were obtained: for suberyldicholine--Km=2.3-10(-5)M, V=2.4 mcM/mg. min, Kss=7.2-10(-2)M; for monocholic ester of suberic acid--Km=7.5-10(-4)M, V=1.5 mcM/mg, min, Kss=1.2-10(-2)M (25 degrees, pH 7.5, 0.1 M KCl). Suberyldicholine was shown to be highly active reversible inhibitor of competitive--non-competitive type (Ki=2.3-10(-6)M, alpha=0.5) of acetylcholinesterase from human erythrocytes; the inhibitory effect of monocholic ester of suberic acid was distinctly lower. By biological and indirect biochemical methods it was found that low concentrations of suberyldicholine 10(-5)=10(-6)M (similar to concentrations that were in an organism upon myorelaxation) were hydrolyzed by acetlycholinesterase with the rate, approximately equal to the rate of acetylcholine hydrolysis. The reversible binding and the enzymatic hydrolysis of suberyldicholine by acetylcholinesterase of tissues were likely to be the main factors that determined the effectiveness and prolonged blocking action of suberyldicholine on the nerve-muscle conductivity.