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The structure of cytochrome b5 reductase, the enzyme that converts methemoglobin to hemoglobin. [1]Methemoglobin (British: methaemoglobin, shortened MetHb) (pronounced "met-hemoglobin") is a hemoglobin in the form of metalloprotein, in which the iron in the heme group is in the Fe 3+ state, not the Fe 2+ of normal hemoglobin.
Spontaneously formed methemoglobin is normally reduced (regenerating normal hemoglobin) by protective enzyme systems, e.g., NADH methemoglobin reductase (cytochrome-b5 reductase) (major pathway), NADPH methemoglobin reductase (minor pathway) and to a lesser extent the ascorbic acid and glutathione enzyme systems. Disruptions with these enzyme ...
In living organisms, because methemoglobin (MetHb) is unable to bind oxygen, it must be reduced to hemoglobin (Hb) through the action of the soluble isoform of cytochrome b5 reductase. Overall, the mechanics of this reaction include electron transfer through oxidation steps, which can be accomplished through a couple of different mechanisms ...
The principal biological role of cytochrome b 5 is reduction of methemoglobin, so cytochrome b 5 deficiency can also result in elevated methemoglobin levels and/or methemoglobinemia, similarly to deficiency of cytochrome b 5 reductase (methemoglobin reductase). [1]
In human blood a trace amount of methemoglobin is normally produced spontaneously; the enzyme methemoglobin reductase is responsible for converting methemoglobin back to hemoglobin. [ 14 ] [ 15 ] Methemoglobinemia can be hereditary but more commonly occurs as a side effect of certain medications or by abuse of recreational drugs .
In biochemistry, the Luebering–Rapoport pathway (also called the Luebering–Rapoport shunt) is a metabolic pathway in mature erythrocytes involving the formation of 2,3-bisphosphoglycerate (2,3-BPG), which regulates oxygen release from hemoglobin and delivery to tissues. 2,3-BPG, the reaction product of the Luebering–Rapoport pathway was first described and isolated in 1925 by the ...
In enzymology, a NADPH—hemoprotein reductase is an enzyme that catalyzes the chemical reaction. NADPH + H + + n oxidized hemoprotein NADP + + n reduced hemoprotein. The three substrates of this enzyme are NADPH, H +, and oxidized hemoprotein, whereas its two products are NADP + and reduced hemoprotein.
This protein-coding gene is a member of the NAD(P)H dehydrogenase (quinone) family and encodes a 2-electron reductase (enzyme). This FAD-binding protein forms homodimers and performs two-electron reduction of quinones to hydroquinones and of other redox dyes.