[A spectrophotometric method for the determination of serum cholinesterase variants with succinyl choline as substrate (author's transl)].

A simple and rapid method for the estimation of the hydrolysis of succinyl choline by serum cholinesterase variants is described. Succinyl choline, as substrate for the enzyme assay, has many advantages over other substrates (acetyl choline, benzoyl choline and butyryl choline) which have no clinical application. Choline, the hydrolytic product of succinyl choline, is oxidized to betaine aldehyde by choline oxidase (EC 1.1.99.1), a rat liver mitochondrial preparation; this is coupled to the reduction of cytochrome c which is measured at 550 nm. Fifty normal sera (UU), 17 heterozygous (UA) and 8 atypical (AA) were tested with this method, and on the basis of resistance to dibucaine (Cinchocain; Kalow, W. & Genest, K. (1957) Canad. J. Biochem. Physiol. 35, 339-346) inhibition, three distinct groups could be established using succinyl choline as substrate. These results are comparable with the standard optical method of Kalow & Genest (cf. above) using benzoyl choline as substrate.