Increased bone marrow delta‐aminolevulinic acid synthetase activity in the acute reversible sideroblastic anemia of alcoholics
. In an effort to clarify the biochemical pathogenesis of the acute reversible siderblastic anemia of alcoholics, bone marrow delta-aminolevulinic acid (ALA) synthetase activity was measured in anemic alcoholic patients with and without pathological ring sideroblasts in their marrows and compared with the activity of this enzyme in normal subjects and in patients with idiopathic sideroblastic anemia. Mean ALA-synthetase activity measured (following addition of exogenous pyridoxal phosphate in three patients with the ring sideroblast morphologic abnormality) was 502 ± 147 (SE) pmoles ALA per 106 erythroblasts per 30 minutes, as compared with 201 ± 69 in the seven alcoholic patients without pathologic sideroblastic marrow abnormalities, 169 ± 32 in the six normal subjects, and 52 ± 4 pmoles ALA per 106 erythroblasts per 30 minutes in two patients with idiopathic sideroblastic anemia. Comparison of enzyme activity in the presence and absence of pyridoxal phosphate revealed that addition of this enzyme cofactor accentuated ALA-synthetase activity by an average of only 24% in the alcoholic sideroblastic group, as compared with 42% accentuation in the normal group and 8% accentuation in the idiopathic sideroblastic group. These results suggest that abnormalities in pyridoxal phosphate metabolism in alcoholics may not be of importance in the inhibition of heme biosynthesis at the level of ALA synthetase but, rather, that an enzymatic or metabolic block should be sought at a more distal site in the heme biosynthetic pathway.