Acquired increases of human erythrocyte purine enzymes

The alterations of three erythrocyte purine enzymes were studied in 12 patients with diseases associated with reticulocytosis, two patients with a partial deficiency of hypoxanthine-guanine phosphoribosyltransferase, seven patients with severe megaloblastic anemia, and 14 normal subjects. The specific activity of adenine phosphoribosyltransferase was positively correlated (r = 0.81) with the reticulocyte percentate in ten patients with a normal hypoxanthine-guanine phosphoribosyltransferase. Two apparent types of alterations of this enzyme were distinguished: (1) increased specific activity with a normal half life as in megaloblastic anemia, and (2) a prolonged half life with or without an elevation of specific activity as in the deficiency of hypoxanthine-guanine phosphoribosyltransferase. Hypoxanthine-guanine phosphoribosyltransferase and phosphoribosylpyrophosphate synthetase were increased in megaloblastic anemia, but were not correlated with the reticulocyte percentage and did not have a consistent change in the half life in the other disorders studied. The data show that acquired disorders associated with reticulocytosis may cause an elevation of the specific activity of purine enzymes in peripheral circulating erythrocytes. Therefore, these factors must be carefully considered in the interpretation of an elevated level of enzyme activity.