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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 ...
Cytochrome b5 reductase is a prevalent topic in research and clinical tests to understand the additional functions of the enzyme in other metabolic pathways in the body. Mice and flies are common model organisms used to test for the relationship of cytochrome b5 reductase with the overall health of living organisms.
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.
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]
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 .
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.
Cytochromes b 5 are ubiquitous electron transport hemoproteins found in animals, plants, fungi and purple phototrophic bacteria.The microsomal and mitochondrial variants are membrane-bound, while bacterial and those from erythrocytes and other animal tissues are water-soluble.