Dihydropteridine reductase deficiency diagnosis by assays on peripheral blood-cells

Human peripheral lymphocytes, granulocytes, and platelets contain the enzyme dihydropteridine reductase. A simple procedure and assay for diagnosing dihydropteridine reductase on peripheral blood is described. In twelve controls the level of enzyme activity in a lymphocyte-platelet preparation was 29.5 +/- 4.8 (SD) nmol NADH oxidised/min/mg protein. Two heterozygotes for dihydropteridine reductase deficiency had activities of 6.4 and 10.3 nmol NADH oxidised/min/mg protein, respectively.