The Cholinesterases in the Light of Recent Findings

Abstract

Purification of enzymes demonstrated that animals possessed 2 distinct cholinesterases. One was specific, hydrolyzing only choline esters, whereas the other hydrolyzed many esters. The former showed a far greater activity at low than at higher concs, of acetylcholine. Its activity-substrate conc, curve was changed at will and even reversed by adding to the enzyme soln. certain organic colloids like protamines which''reversed the electric charge of the enzyme particles. This did not alter the enzyme specificity which was the only criterion to differentiate cholinesterases. Non-specific pseudo-cholin-esterase was found to be of lesser physiologic importance. It was absent from ox and sheep blood or tissues, and reduction of its activity by feeding rats 5 g./kg. of tri-ortho-cresyl-phosphate caused no obvious functional changes.