抄録
A new method for the determination of δ-aminolevulinic acid (ALA) synthetase activity in human erythroblasts has been developed. ALA synthetase in erythroblasts was partially purified so as to permit the use of 14C-succinyl-CoA as the precursor for the enzyme. The partially purified enzyme solution contained negligible activity of succinyl-CoA hydrolase. It also contained negligible or very low activity of succinyl-CoA synthetase and a-ketoglutarate dehydrogenation complex. After incubation at 37° for 30 min, 14C-ALA formed was isolated by Dowex 50W x 8 column. Radioactivity in the eluate from the column was proved by paperchromatography to be exclusively derived from IC-ALA. Only 20-30 % of the activity was lost in the course of enzyme purification. All the procedure requires only 4 hours. ALA synthetase activity in the erythroblasts of patients with several hematological disorders was determined by this new assay method. ALA synthetase activity in the erythroblasts of patients with iron deficiency anemia was normal or slightly elevated. Almost all cases of primary sideroblastic anemia showed decreased ALA synthetase activity. ALA synthetase froma case of primary acquired sideroblastic anemia had a Km for the pyridoxal phosphate 10 foldlarger than normal. A son of patient with congenital sideroblastic anemia showed decreased ALA synthetase activity. The enzyme activity was also decreased in the erythroblasts from patients with pyridoxine responsive anemia. However, the enzyme activity gradually increased in the course of treatment with pyridoxine. Apo-ALA synthetase was decreased in the two cases of pyridoxine responsive anemia.
