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methemoglobin (MetHb, Hi)
Hemoglobin with oxidized or ferric heme (Fe+3). Normal methemoglobin content of erythrocytes is < 1-1.5%. A small amount of methemoglobin is always being produced, but is reduced back to hemoglobin by the NADH methemoglobin reducatase system (largely NADH cytochrome-b5 reductase & to a lesser extent ascorbate, glutathione & NADPH methemoglobin reductase). Methemoglobin combines strongly with cyanide, sulfide, peroxides, fluoride, & azide.
Related
methemoglobinemia
General
hemoglobin
Properties
COMPARTMENT: cytoplasm
CELL: erythrocyte
SUBUNITS: hemoglobin alpha chain
:MOTIF_INHERITANCE SHADOW
:MOTIF heme-binding site
:COFACTOR_BOUND heme
:METAL Fe+3
:QUANTITY 2
hemoglobin beta chain
:MOTIF_INHERITANCE SHADOW
:MOTIF heme-binding site
:COFACTOR_BOUND heme
:METAL Fe+3
:QUANTITY 2
References
- Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed)
Lippincott-Raven, Philadelphia, 1998, pg 791
- Henry's Clinical Diagnosis & Management by Laboratory Methods,
21st edition, McPherson RA & Pincus MR (es), W.B. Saunders Co.,
Philadelphia, PA. 2007, 457