The inhibition of serum cholinesterase by urea. Mechanism of action and application in the typing of abnormal genes.

The mechanism of action of urea on serum cholinesterase and the application of the inhibition by urea in the typing of the abnormal genes of this enzyme were investigated. Urea caused a competitive, irreversible inhibition of serum cholinesterase, which was most pronounced for the abnormal enzymes. Urea inhibition, used with dibucaine inhibition, allowed differentiation between all the known genotypes of locus E1. In the differentiation of rarer genotypes, the combination of urea numbers (percentage inhibition of serum cholinesterase activity caused by urea 5 mol litre-1) and dibucaine numbers was found, in certain situations, to be superior to the classical combination of fluroide and dibucaine numbers.