A new, specific, and simple method for the determination of δ-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 [14C]succinyl-CoA as a substrate for this enzyme. In this enzyme preparation there were negligible activities of succinyl-CoA hydrolase, α-ketoglutarate dehydrogenase, and succinyl-CoA synthetase and there was no activity of ALA dehydrase.
