Human serum contains EDTA-sensitive (Ca ++ -dependent) and EDTA-stable (albumin) paraoxonases which hydrolyse paraoxon, 0,0-diethyl,0-4-nitrophenyl phosphate.In Caucasians the EDTA-sensitive enzyme shows a genetically determined polymorphism which is governed by two alleles. In typical Mongoloid or Negro populations this polymorphism is expressed to a lesser degree, and in a few samples (e.g. Aborigines) it cannot be observed at all. The distribution of the activity of the EDTAstable (albumin) paraoxonase is unimodal.Many authors supposed that paraoxonase is an arylesterase (EC 3.1.1.2) which means that it is also able to hydrolyse phenylacetate or β-naphthylacetate. New investigations have shown that the human serum fractions splitting paraoxon can be separated from those hydrolysing phenylacetate and related substrates.The polymorphism of the EDTA-sensitive human serum paraoxonase can be applied to investigations concerning specificity. From this it becomes evident that this enzyme is rather specific. Already slight changes of the paraoxon molecule lead to a decrease of activity. On the other hand the enzyme seems to hydrolyse also phosphonic acid esters and 4-nitrophenylacetate in the same way like paraoxon (polymorphism).There is a linkage relationship of paraoxonase with cystic fibrosis and DNA markers. According to these results the (EDTA-sensitive) paraoxonase locus is on the human chromosome 7.A high serum paraoxonase level actually protects serum cholinesterase (EC 3.1.1.8) and has to be considered in biological monitoring of workers exposed to parathion.

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The enzyme serum paraoxonase shows a polymorphism in Europeans which is governed by two alleles. The first allele has a gene frequency plow of 0.716-0.777, and is manifested as a low activity group in homozygotes. More than 50% of all European test subjects can be included in this group. A second allele with a gene frequency qhigh of 0.223-0.284 was found in typical European distributions and is manifested in both the form of a second heterozygotic and a third homozygotic group with high activities. The Hardy-Weinberg rule for a two-allele model is valid for the distribution. The gene frequency plow of the first allele decreases as one moves from Europe in the direction of Africa and Asia. In typical Mongoloid and Negroid collectives, less than 10% of the population can be included in the low-activity group, a group which is not even demonstrable in the Aborigines of Australia. The serum paraoxonase of the Aborigine population shows unimodal distribution. The validity of the Hardy-Weinberg rule for a three-allele model must be rejected in all examined collectives. Human serum paraoxonase shows neither age-related changes in activity nor sex-dependent activity differences.

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A retrospective on the remarkable life of the female Professor of Dermatology in Germany. She was best known for her studies of fungal diseases of the skin. The article is based on personal recollections of her daughter and a comprehensive study of her scientific work.