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The overall reduction reaction from cytochrome b5 reductase aids in the control of iron in red blood cells, which dictates the amount of oxygen cells carry. [ 3 ] Cytochromes are redox proteins that are essential for energy transfer in the electron transport chain with the help of an enzyme such as a reductase .
Also, vitamin C can occasionally reduce cyanosis associated with chronic methemoglobinemia, and may be helpful in settings in which methylene blue is unavailable or contraindicated (e.g., in an individual with G6PD deficiency). [22] Diaphorase (cytochrome b5 reductase) normally contributes only a small percentage of the red blood cell's ...
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]
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.
A methemoglobin level > 1.5 g/dL causes cyanosis. The most common congenital cause is a deficiency in the enzyme cytochrome b5 reductase which reduces methemoglobin in the blood. [22] However, in infants the most common cause of methemoglobinemia is acquired through the ingestion of nitrates (NO − 3) through well water or foods.
Mutations in the CYB5R3 gene cause methemoglobinemia types I and II. This is a rare autosomal recessive disease due to a deficiency of isoform of NADH-cytochrome b5 reductase. [13] Many mutations of this gene and the subsequent disease manifestation have been described. [14] The disease manifests as the accumulation of oxidized Fe+3 in humans. [10]
In human blood a trace amount of methemoglobin is normally produced spontaneously; the enzyme methemoglobin reductase is responsible for converting methemoglobin back to hemoglobin. [ 23 ] [ 24 ] Methemoglobinemia can be hereditary but more commonly occurs as a side effect of certain medications or by abuse of recreational drugs .
Hemoglobin M disease is a rare form of hemoglobinopathy, characterized by the presence of hemoglobin M (HbM) and elevated methemoglobin (metHb) level in blood. [1] HbM is an altered form of hemoglobin (Hb) due to point mutation occurring in globin-encoding genes, mostly involving tyrosine substitution for proximal (F8) or distal (E7) histidine residues. [2]