An improved method for phenotyping individuals for the human serum paraoxonase arylesterase polymorphism

Human serum paraoxonase/arylesterase is a polymorphic enzyme, determined by two allelic genes at one autosomal locus. These two isozymes are called (A) and (B), and the three corresponding phenotypes A, AB and B. We measure paraoxon hydrolysis (paraoxonase activity), with, or without 1 M NaCl, and phenylacetate hydrolysis (arylesterase activity) with, or without 0.1 mM chlorpromazine. The resulting four measurements make it possible to determined essentially every individual's phenotype. The combination of qualitative tests, based on distinctive characteristics of the two isozymes, greatly improves our ability to determine individual phenotypes and detect other isozymic variants of the esterase. For several years, we have been interested in the possible correlation of the phenotypes of paraoxonase/arylesterase and sensitivity or resistance to organophosphate exposure [1]. Recent reports show that the paraoxonase gene may be closely linked to the gene for cystic fibrosis [2]. If this will be confirmed, it could be another very practical reason for typing people for this polymorphic marker. Being able to identify those heterozygous for the paraoxonase/arylesterase polymorphism, about 43% of the European population, should greatly enhance the value of phenotyping for this simple, convenient, polymorphic trait.