Identification of the E 1 fElk cholinesterase genotype

Since the introduction of the short acting muscle relaxant succinyl dicholine (suxamethonium) in 1951 and the subsequent discovery that certain patients exhibited a greater than usual sensitivity to the drug, interest has been directed towards identifying the genetically controlled variants of serum cholinesterase (acylcholine acyl hydrolase E.C. 3.1.1.8). Some of these variants have been found to be the biochemical basis for this prolonged relaxant effect. The atypical, dibucaine resistant variant described in 1957 by Kalow and Genest,' the fluoride resistant variant identified by Harris and Whittaker2 in 1961, and the silent gene reported in 1962 by Liddell et a13 were the first cholinesterase variants to be recognised. Taken in pairs, these three variants, together with the usual gene, result in 10 possible cholinesterase genotypes, all of which have been described and identified. In 1976, Garry et a14 identified the J allele, while two years later Rubinstein et a15 reported the K allele. These are both quantitative