On genetically determined human serum cholinesterases.

The existence of genetically determined human serum cholinesterase variants (actlcholine acyl-hydrolase; EC 3.1.1.8) has been recognized by the use of a short acting muscle relaxant, suxamethonium. This polymorphism is now explained by at least four alleles belonging to an autosomal locus Ch1 or E1 depending on the nomenclature. These are: the usual gene, the dibucaine-resistant gene, the fluoride-resistant gene and the silent gene. At present, the modes of transmission for the silent genes is confusing and lack proper understanding. Another variant, not an allele of the first group, is recognized by gel electrophoresis, belong to a second locus Ch2 or E2. Evidence has been presented that many more rare serum cholinesterase variants may exist. Besides these genetic variants, normal serum cholinesterase is known to exist in multiple molecular forms. The present article attempts to discuss the polymorphism of human cholinesterase in relation to their chemical and genetic characteristics and their possible function.