title: Enzymatic reduction of hemoglobins M.
abstract: Reductions of five species of hemoglobins (Hb1) M by two methemoglobin reductases and by ferredoxin and ferredoxin-NADP reductase were studied under anaerobic conditions. Abnormal chains of Hb M Milwaukee and Hb M Saskatoon were reduced by NADH-cytochrome b5 reductase (= NADH-methemoglobin reductase) highly purified from human erythrocytes. Hb M Saskatoon was also reduced by an another enzyme in red cells, NADPH-flavin reductase (= NADPH-methemoglobin reductase). All Hbs M with a beta chains anomaly such as Hb M Hyde Park, Hb M Saskatoon, and Hb M Milwaukee were reduced by ferredoxin and ferredoxin-NADP reductase. These three enzymatic reduction systems did not reduce Hbs M with an alpha chain anomaly such as Hb M Iwate and Hb M Boston. These differences in the reduction are discussed in relation to the redox potential of each abnormal chain in methemoglobin M.
mesh_terms: D042966:Cytochrome-B(5) Reductase / Q000378:metabolism*; D005287:Ferredoxin-NADP Reductase / Q000378:metabolism*; D005288:Ferredoxins / Q000378:metabolism*; D006449:Hemoglobin M / Q000378:metabolism*; D006455:Hemoglobins, Abnormal / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D010084:Oxidation-Reduction; D013053:Spectrophotometry; D013329:Structure-Activity Relationship
chemical_list: D005288:Ferredoxins; D006455:Hemoglobins, Abnormal; D006449:Hemoglobin M; D005287:Ferredoxin-NADP Reductase; D009247:NADH, NADPH Oxidoreductases; D042966:Cytochrome-B(5) Reductase