Assay of Serum Cholinesterase with Succinylcholine and Propionylthiocholine as Substrates

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Abstract
Serum cholinesterase (EC 3.1.1.8) was assayed with succinylcholine as a substrate. The reaction was coupled with choline oxidase and peroxidase in the presence of 4-aminoantipyrine and phenol to produce a red quinone dye that was measured spectrophotometrically. The method requires 25 .mu.l of sample in a total volume of 1.0 ml. The mean activity for 35 adults of the usual genotype was 74.4 .+-. 28 U/l (range 24-125 U/l). Succinylcholine-sensitive individuals had activities below 18 U/l. The same serum samples also were assayed with propionylthiocholine as a substrate. Activities with the 2 substrates showed a coefficient of correlation of 0.980 (n = 68). The method using propionylthiocholine showed more overlap between the activities of succinylcholine-sensitive and insensitive individuals. Assay with succinylcholine thus may offer a more effective method of screening for sensitive individuals, since some escape detection by conventional genotyping with dibucaine and fluoride.