Human biochemical genetics of plasma dopamine-beta-hydroxylase and erythrocyte catechol-o-methyltransferase.

The purpose of the studies reviewed here was to investigate the role of inheritance in the regulation of human plasma dopamine-beta-hydroxylase (DBH) and human erythrocyte (RBC) catechol-O-methyltransferase (COMT) activities. DBH is a catecholamine biosynthetic enzyme and COMT is catecholamine metabolic enzyme. It has been suggested that the level of the activities of these enzymes in human blood might reflect the function or status of the adrenergic nervous system. Both enzyme activities were measured in blood samples from large, randomly selected populations of children, adolescents, and adults, and in the blood of first-degree relatives of subjects with either very low plasma DBH activity (less than 50 U/ml) or very low RBC COMT activity (less than 8U/ml). A radioimmunoassay for human plasma DBH was also used in these studies. The results of sibship and pedigree analyses of data from families of probands with very low enzyme activities were compatible with the autosomal recessive inheritance of an allele for very low plasma DBH activity that results in a decrease in DBH protein in plasma, and the autosomal recessive inheritance of an allele for low erythrocyte COMT activity.