Pyridoxine-responsive primary acquired sideroblastic anaemia. In vitro and in vivo effects of vitamin B6 on decreased 5-aminolaevulinate synthase activity.
The activity of 5-aminolaevulinate (ALA) synthase, the first and rate-limiting of haem synthesis, was markedly reduced (13% of controls) in erythroblasts of a patient with acquired, primary sideroblastic anaemia (PASA). The reduced activity of ALA synthase could not be restored in vitro with 1 mmol/l pyridoxal-5-phosphate (PLP). Treatment of the patient with pyridoxine for several months increased the ALA synthase activity from 13% to 50% of controls in the absence and to 100% in the presence of PLP in the incubation medium. These studies suggest that both increased degradation of apo-ALA synthase and decreased affinity of ALA synthase for PLP may be involved in pyridoxine-responsive PASA.
D000624:5-Aminolevulinate Synthetase / Q000097:blood*; D000328:Adult; D000368:Aged; D000756:Anemia, Sideroblastic / Q000188:drug therapy*; D004900:Erythroblasts / Q000201:enzymology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011732:Pyridoxal Phosphate / Q000494:pharmacology; D011736:Pyridoxine / Q000494:pharmacology / Q000627:therapeutic use*
D011732:Pyridoxal Phosphate; D000624:5-Aminolevulinate Synthetase; D011736:Pyridoxine