Abnormal red-cell metabolism of pyridoxine associated with beta-thalassaemia.
Red-cell conversion of pyridoxine to pyridoxal phosphate was studied in control subjects, and patients with heterozygous and homozygous beta-thalassaemia. In 7% of control subjects the rate of pyridoxine conversion was well below the range found in the other control subjects (5.0-8.6%, mean 6.5%/g Hb x 10(-2)) but in heterozygous beta-thalassaemia was below that range in 63% of the patients. The conversion rate was also slow or borderline in the majority of patients with severe transfusion-dependent homozygous beta-thalassaemia, in spite of the presence of some donor cells; but was normal, or fast as in other anaemias, in all but one patient with mild homozygous thalassaemia. There was a much higher incidence of a slow conversion rate in the parents of the severe homozygotes than in parents of the mild homozygotes, illustrating the familial pattern. This supports our view that the red-cell conversion rate of pyridoxine is an inherited characteristic, independent of thalassaemia. The cause of a reduced rate of pyridoxine conversion was investigated. The increase to a normal rate following riboflavin ingestion suggests a defect in the activity of the flavin mononucleotide (FMN)-dependent pyridoxine phosphate oxidase.
D000255:Adenosine Triphosphate / Q000097:blood; D000293:Adolescent; D000328:Adult; D000368:Aged; D002675:Child, Preschool; D004912:Erythrocytes / Q000378:metabolism*; D005260:Female; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D011732:Pyridoxal Phosphate / Q000097:blood; D011734:Pyridoxaminephosphate Oxidase / Q000097:blood; D011736:Pyridoxine / Q000097:blood*; D013789:Thalassemia / Q000097:blood*
D011732:Pyridoxal Phosphate; D000255:Adenosine Triphosphate; D011734:Pyridoxaminephosphate Oxidase; D011736:Pyridoxine