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Methemoglobinemia, or methaemoglobinaemia, is a condition of elevated methemoglobin in the blood. [2] Symptoms may include headache, dizziness, shortness of breath, nausea, poor muscle coordination, and blue-colored skin (cyanosis). [2]
The most common and successful treatment used to treat patients with high levels of methemoglobinemia is the antidote methylene blue. Methylene blue is already recognized as a product of the reversible reaction fueled by NAPHD methemoglobin reductase, catalyzed by leukcomethylene, to reduce methemoglobin to hemoglobin.
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.
Methemoglobinemia is also an uncommon cause of drug-induced nonautoimmune hemolytic anemia. In methemoglobinemia, drug-induced oxidative stress causes the oxidation of the Fe 2+ ion within the heme molecule in hemoglobin to Fe 3+, forming excessive amounts of methemoglobin.
Methemoglobinemia is a condition caused by elevated levels of methemoglobin in the blood. Methaemoglobin is a form of hemoglobin that contains the ferric [Fe 3+] form of iron, instead of the ferrous [Fe 2+] form . Methemoglobin cannot bind oxygen, which means it cannot carry oxygen to tissues.
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.
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]
Methemoglobin is also formed in small quantities when the dissociation of oxyhemoglobin results in the formation of methemoglobin and superoxide, O 2 −, instead of the usual products. Superoxide is a free radical and causes biochemical damage, but is neutralised by the action of the enzyme superoxide dismutase.