Letter | Published:

Incidence of Pseudocholinesterase Variants in Australian Aborigines

Naturevolume 199page1115 (1963) | Download Citation



THERE are now known to be a number of genetically determined variants of the human serum enzyme pseudocholinesterase1–5, of which the most frequent in Britain are the ‘typical’ and ‘atypical’ variants. Homozygotes for the ‘typical’ variant amount to about 96 per cent of the population, and heterozygotes to about 4 per cent. ‘Atypical’ homozygotes are only seen once among several thousands. The different pseudocholinesterase types are recognized by determining the degree of inhibition of the enzyme by dibucaine (‘Nupercaine’) following the method of Kalow and Genest1, the percentage inhibition being called the dibucaine number. The other pseudocholinesterase variants are extremely rare and they are also discovered in the first instance by their less than normal inhibition by dibucaine, with one exception, the ‘silent’ variant4 which in the homozygote results in complete absence of enzyme activity.

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  1. Commonwealth Health Laboratory, Cairns, Queensland

    • W. R. HORSFALL
  2. St. Bartholomew's Hospital, London, E.C.1

    • H. LEHMANN


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