The human liver and reticulocyte cytochrome b5 mRNAs are products from a single gene

Giordano, Sara J.; Steggles, Alan W.

doi:10.1016/0006-291x(91)91776-9

Cited by 36 publications

(11 citation statements)

References 10 publications

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“…Activity results are from three experiments each performed in duplicate. isoforms of cyt b5 are the product of a single gene (Giordano and Steggles, 1991). Together cyt b5 and b5R mediate electron transfer from NADH to fatty acid desaturases (Oshino et al, 1971) and P450 oxidases (Hildebrandt and Estabrook, 1971) and, in erythrocytes, play a primary role in the maintenance of hemoglobin in its reduced state (Hultquist and Passon, 1971).…”

Section: Discussionmentioning

confidence: 99%

NADH Cytochromeb₅Reductase and Cytochromeb₅Catalyze the Microsomal Reduction of Xenobiotic Hydroxylamines and Amidoximes in Humans

Kurian

Bajad²,

Miller³

et al. 2004

J Pharmacol Exp Ther

105

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Hydroxylamine metabolites, implicated in dose-dependent and idiosyncratic toxicity from arylamine drugs, and amidoximes, used as pro-drugs, are metabolized by an as yet incompletely characterized NADH-dependent microsomal reductase system. We hypothesized that NADH cytochrome b 5 reductase and cytochrome b 5 were responsible for this enzymatic activity in humans. Purified human soluble NADH cytochrome b 5 reductase and cytochrome b 5 , expressed in Escherichia coli, efficiently catalyzed the reduction of sulfamethoxazole hydroxylamine, dapsone hydroxylamine, and benzamidoxime, with apparent K m values similar to those found in human liver microsomes and specific activities (V max ) 74 to 235 times higher than in microsomes. Minimal activity was seen with either protein alone, and microsomal protein did not enhance activity other than additively. All three reduction activities were significantly correlated with immunoreactivity for cytochrome b 5 in individual human liver microsomes. In addition, polyclonal antibodies to both NADH cytochrome b 5 reductase and cytochrome b 5 significantly inhibited reduction activity for sulfamethoxazole hydroxylamine. Finally, fibroblasts from a patient with type II hereditary methemoglobinemia (deficient in NADH cytochrome b 5 reductase) showed virtually no activity for hydroxylamine reduction, compared with normal fibroblasts. These results indicate a novel direct role for NADH cytochrome b 5 reductase and cytochrome b 5 in xenobiotic metabolism and suggest that pharmacogenetic variability in either of these proteins may effect drug reduction capacity.Hydroxylamine and amidoxime compounds are metabolized in humans by an as yet incompletely characterized NADH-dependent reductase system. Hydroxylamine metabolites have been implicated in dose-dependent and idiosyncratic drug toxicity from sulfamethoxazole, dapsone, procainamide, and other arylamine drugs (Uetrecht, 2002). Amidoximes and other hydroxylated amines have been developed as prodrugs to enhance the absorption of a wide range of antihypertensive, antiprotozoal, and antithrombotic drugs (Weller et al

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Section: Discussionmentioning

confidence: 99%

NADH Cytochromeb₅Reductase and Cytochromeb₅Catalyze the Microsomal Reduction of Xenobiotic Hydroxylamines and Amidoximes in Humans

Kurian

Bajad²,

Miller³

et al. 2004

J Pharmacol Exp Ther

105

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“…The coding region of human NR1 was investigated by direct sequencing of PCR products derived from two overlapping cDNA fragments using published primers (5). The coding region of human soluble cytochrome b 5 gene was investigated by direct sequencing in both directions of PCR products derived from cDNA using primers containing the 15 nucleotides specific to the soluble isoform (26).…”

Section: Co]cbl Was Determined In Intact Fibroblasts As Described Earmentioning

confidence: 99%

The cblD Defect Causes Either Isolated or Combined Deficiency of Methylcobalamin and Adenosylcobalamin Synthesis

Suormala

Baumgartner

Coelho

et al. 2004

Journal of Biological Chemistry

112

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Intracellular cobalamin is converted to adenosylcobalamin, coenzyme for methylmalonyl-CoA mutase and to methylcobalamin, coenzyme for methionine synthase, in an incompletely understood sequence of reactions. Genetic defects of these steps are defined as cbl complementation groups of which cblC, cblD (described in only two siblings), and cblF are associated with combined homocystinuria and methylmalonic aciduria. Here we describe three unrelated patients belonging to the cblD complementation group but with distinct biochemical phenotypes different from that described in the original cblD siblings. Two patients presented with isolated homocystinuria and reduced formation of methionine and methylcobalamin in cultured fibroblasts, defined as cblD-variant 1, and one patient with isolated methylmalonic aciduria and deficient adenosylcobalamin synthesis in fibroblasts, defined as cblD-variant 2. Cell lines from the cblD-variant 1 patients clearly complemented reference lines with the same biochemical phenotype, i.e. cblE and cblG, and the cblD-variant 2 cell line complemented cells from the mutant classes with isolated deficiency of adenosylcobalamin synthesis, i.e. cblA and cblB. Also, no pathogenic sequence changes in the coding regions of genes associated with the respective biochemical phenotypes were found. These findings indicate heterogeneity within the previously defined cblD mutant class and point to further complexity of intracellular cobalamin metabolism.

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“…The 130-residue N-terminal domain bears strong homology to classic microsomal cytochrome b 5 , a sixcoordinate heme protein. At the C terminus, there is a 300-residue domain with strong homology to classic microsomal cytochrome b 5 reductase, a flavoprotein. Ncb5or is of special interest because it is highly conserved in a wide range of animals from mammals to flies and worms and because there is no other example in the animal kingdom of such a two-domain protein.…”

mentioning

confidence: 99%

“…Ncb5or (alternatively called b5ϩb5R and cyb5r4) is a single 58-kDa polypeptide composed of two well characterized domains tethered by a unique 90-residue hinge (1). The 130-residue N-terminal domain bears strong homology to classic microsomal cytochrome b 5 , a sixcoordinate heme protein. At the C terminus, there is a 300-residue domain with strong homology to classic microsomal cytochrome b 5 reductase, a flavoprotein.…”

mentioning

confidence: 99%

Loss of Ncb5or Results in Impaired Fatty Acid Desaturation, Lipoatrophy, and Diabetes

Larade

Jiang

Zhang

et al. 2008

Journal of Biological Chemistry

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Targeted ablation of the novel flavoheme reductase Ncb5or knock-out (KO) results in progressive loss of pancreatic ␤-cells and white adipose tissue over time. Lipoatrophy persisted in KO animals in which the confounding metabolic effects of diabetes were eliminated by islet transplantation (transplanted knockout (TKO)). Lipid profiles in livers prepared from TKO animals were markedly deficient in triglycerides and diacylglycerides. Despite enhanced expression of stearoyl-Co-A desaturase-1, levels of palmitoleic and oleic acids (⌬9 fatty acid desaturation) were decreased in TKO relative to wild type controls. Treatment of KO hepatocytes with palmitic acid reduced cell viability and increased apoptosis, a response blunted by coincubation with oleic acid. The results presented here support the hypothesis that Ncb5or supplies electrons for fatty acid desaturation, offer new insight into the regulation of a crucial step in fatty acid biosynthesis, and provide a plausible explanation for both the diabetic and the lipoatrophic phenotype in Ncb5or ؊/؊ mice.The most prevalent and life-threatening metabolic disorders, type 2 diabetes and obesity, arise from the complex interplay of a large number of genetic determinants. Characterizing polygenic disorders is challenging, requiring insight into plausible candidate genes and analysis of genomic data on numerous kindred. Mouse models offer an attractive independent source of information on genes important in pancreatic ␤-cell and adipocyte viability and homeostasis.We have been investigating a novel flavoheme reductase that plays an important role in pancreatic ␤-cell viability and maintenance of white adipose tissue. Ncb5or (alternatively called b5ϩb5R and cyb5r4) is a single 58-kDa polypeptide composed of two well characterized domains tethered by a unique 90-residue hinge (1). The 130-residue N-terminal domain bears strong homology to classic microsomal cytochrome b 5 , a sixcoordinate heme protein. At the C terminus, there is a 300-residue domain with strong homology to classic microsomal cytochrome b 5 reductase, a flavoprotein. Ncb5or is of special interest because it is highly conserved in a wide range of animals from mammals to flies and worms and because there is no other example in the animal kingdom of such a two-domain protein.Ncb5or is expressed in a wide variety of organs, tissues, and cell lines and localized in the endoplasmic reticulum (2). Because of its high negative redox potential, Ncb5or would be expected to function primarily as an electron donor.Mice with a global knock-out of Ncb5or have normal embryonic and fetal development and normal viability at birth with no gross anatomic abnormalities (3). However, after the first month of life, Ncb5or Ϫ/Ϫ mice develop diabetes because of the loss of pancreatic ␤-cells. In addition, there is progressive atrophy of white adipose tissue (WAT).3 The diabetic and lipoatrophic phenotype of the Ncb5or Ϫ/Ϫ mouse raises the question of how this novel reductase impacts ␤-cell and adipocyte viability and function."Class...

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The human liver and reticulocyte cytochrome b5 mRNAs are products from a single gene

Cited by 36 publications

References 10 publications

NADH Cytochromeb₅Reductase and Cytochromeb₅Catalyze the Microsomal Reduction of Xenobiotic Hydroxylamines and Amidoximes in Humans

NADH Cytochromeb₅Reductase and Cytochromeb₅Catalyze the Microsomal Reduction of Xenobiotic Hydroxylamines and Amidoximes in Humans

The cblD Defect Causes Either Isolated or Combined Deficiency of Methylcobalamin and Adenosylcobalamin Synthesis

Loss of Ncb5or Results in Impaired Fatty Acid Desaturation, Lipoatrophy, and Diabetes

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The human liver and reticulocyte cytochrome b5 mRNAs are products from a single gene

Cited by 36 publications

References 10 publications

NADH Cytochromeb5Reductase and Cytochromeb5Catalyze the Microsomal Reduction of Xenobiotic Hydroxylamines and Amidoximes in Humans

NADH Cytochromeb5Reductase and Cytochromeb5Catalyze the Microsomal Reduction of Xenobiotic Hydroxylamines and Amidoximes in Humans

The cblD Defect Causes Either Isolated or Combined Deficiency of Methylcobalamin and Adenosylcobalamin Synthesis

Loss of Ncb5or Results in Impaired Fatty Acid Desaturation, Lipoatrophy, and Diabetes

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NADH Cytochromeb₅Reductase and Cytochromeb₅Catalyze the Microsomal Reduction of Xenobiotic Hydroxylamines and Amidoximes in Humans

NADH Cytochromeb₅Reductase and Cytochromeb₅Catalyze the Microsomal Reduction of Xenobiotic Hydroxylamines and Amidoximes in Humans