Involvement of oxidoreductive reactions of intracellular haemoglobin in the metabolism of 3-hydroxyanthranilic acid in human erythrocytes

3-Hydroxyanthranilic acid, a metabolite of tryptophan, was rapidly metabolized by human erythrocytes. The final product was determined to be cinnabarinic acid as detected by spectrophotometry, paper chromatography and t.l.c. The formation of cinnabarinic acid from 3-hydroxyanthranilic acid in the cells was markedly inhibited by CO when intracellular haemoglobin was in a ferrous state, and by cyanide when it was in a ferric state. Ferrous haemoglobin in erythrocytes was oxidized to (alpha 3+ beta 2+)2, (alpha 2+ beta 3+)2 and (alpha 3+ beta 3+)2 by 3-hydroxyanthranilic acid, and the oxidation rates were very high, like those of cinnabarinic acid formation, suggesting that the metabolism of 3-hydroxyanthranilic acid is coupled with oxidoreductive reactions of intracellular haemoglobin. This view was further confirmed by the findings that 3-hydroxyanthranilic acid was metabolized by ferrous or ferric haemoglobin and that ferrous and ferric haemoglobins were oxidized and reduced by the compound respectively. The significance of the metabolism of 3-hydroxyanthranilic acid and the oxidoreductive reactions of haemoglobin with this compound may be associated with the pathological conditions with increased 3-hydroxyanthranilic acid levels in the blood of diabetic subjects.