An improvement in segregation of human butyrylcholinesterase phenotypes having the fluoride-resistant variants

Correct recognition of butyrylcholinesterase (BChE; EC 3.1.1.8) variants in human serum is essential if patients susceptible to a prolonged reaction following treatment with short acting muscle relaxants, like suxamethonium, are to be reliably identified. The dimethylcarbamate Ro 02-0683 is used in standard procedures for identification of BChE variant by measuring residual activity after two hours of inhibition. Such a long inhibition time distinguishes well between the usual (U) and atypical (A), but less successfully the fluoride-resistant (F) variant. In this paper, inhibition rate constants were determined from the initial time course of inhibition of homozygous (FF) and heterozygous (UF and AF) BChE phenotypes by Ro 02-0683; 1.6 x 10(6), 2.7 x 10(6) and 6.2 x 10(6) dm3 mol-1 min-1 for AF, FF and UF, respectively. After only 30 min of inhibition the resolution between the phenotypes was even better than after two hours. Hence, determination of the residual activity after 30 min inhibition is recommended for the segregation of the suxamethonium sensitive fluoride-resistant variants.