Cytochrome b5 reductase | definition of cytochrome b5 reductase by Medical dictionary
cytochrome b5 reductase
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cy·to·chrome b5 re·duc·tase (sī'tō-krōm rē-dŭk'tās),
A flavoenzyme catalyzing the reduction of two molecules of ferricytochrome b5 to two molecules of ferrocytochrome b5 at the expense of NADH; has a role in fatty acid desaturation; a deficiency can lead to hereditary methemoglobinemia (type I, only observed in erythrocyte cytosol; type II, deficiency in all tissues; type III, deficiency in all hematopoetic cells).
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TABLE 1 Types of cytochrome b5 reductase
efficiency Type % of Cases with deficiency Clinical Features I 85-90% Cyanotic usually asymtomatic, normal survival and pregnancies, can develop toxic levels of metHb when affected by exposure to drugs II 10-15% Severe and fatal, associated with neurological and skeletal abnormalities III Rare Intermediate in severity between I and II IV Rare Type Level of metHb Site of Defect I 20-40% Decreased RBC NADH-dependent metHb reductase II ??