Measurement of delta-aminolevulinic acid synthetase activity in human erythroblasts

A new, specific, and simple method for the determination of delta-aminolevulinic acid (ALA) synthetase activity in human bone marrow cells has been developed. ALA synthetase of erythroblasts was partially purified so as to permit the use of [(14)C]succinyl-CoA as a substrate for this enzyme. In this enzyme preparation there were negligible activities of succinyl-CoA hydrolase, alpha-ketoglutarate dehydrogenase, and succinyl-CoA synthetase and there was no activity of ALA dehydrase. The ALA formed from [(14)C]succinyl-CoA has been isolated by column chromatography. Radioactivity in the eluate from the column has been proved by paper chromatography to be exclusively that of [(14)C]ALA. The entire assay can be completed within 4 h, and [(14)C]succinyl-CoA was incorporated into [(14)C]ALA on the order of several percent. Moderate to marked decreases of ALA synthetase activity have been demonstrated in the erythroblasts of all cases of sideroblastic anemia. In the cases of iron deficiency anemia, on the other hand, normal or slightly elevated activity has been obtained.