EVALUATION OF THE DECARBAMYLATION PROCESS OF CHOLINESTERASE DURING ASSAY OF ENZYME-ACTIVITY

The activity of carbamylated cholinesterase increases continuously dur ing assay, suggesting that progressive decarbamylation takes place. Th e following effects of assay conditions oil the observed decarbamylati on were studied: the effect of the sulfhydryl group of nitrobenzoate p roduced in the course of Ellman assay, the effect of substrate and the effect of sample dilution during assay, This study indicates that sam ple dilution is the main trigger to the dacarbamylation observed durin g assay of cholinesterase activity. The process was described as a fir st-order reaction during which the inhibited enzyme gives place to the active form. Kinetic constants for decarbamylation of human pseudocho linesterase (EC 3.1.1.8) at 30 degrees C were approximately 0.005 min( -1) for dimethylcarbamates and 0.010 min(-1) for monomethylcarbamates, when 1 mmol/l propionylthiocholine was used as substrate.