The Experts below are selected from a list of 105 Experts worldwide ranked by ideXlab platform
Bernd Clement - One of the best experts on this subject based on the ideXlab platform.
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DMD #5249 1
2016Co-Authors: Bernd Clement, Sabine Mau, Stephanie Deters, Antje HavemeyerAbstract:Hepatic, extrahepatic, microsomal, and mitochondrial activation of the N-hydroxylated prodrugs Benzamidoxime, guanoxabenz, and Ro 48-365
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The N-Reductive System Composed of Mitochondrial Amidoxime Reducing Component (mARC), Cytochrome b5 (CYB5B) and Cytochrome b5 Reductase (CYB5R) Is Regulated by Fasting and High Fat Diet in Mice
2016Co-Authors: Heyka H. Jakobs, Antje Havemeyer, Michal Mikula, Adriana Strzalkowska, Artur Dzwonek, Marta Gajewska, Ewa E. Hennig, Jerzy Ostrowski, Monika Borowa, Bernd ClementAbstract:The mitochondrial amidoxime reducing component mARC is the fourth mammalian molybdenum enzyme. The protein is capable of reducing N-oxygenated structures, but requires cytochrome b5 and cytochrome b5 reductase for electron transfer to catalyze such reactions. It is well accepted that the enzyme is involved in N-reductive drug metabolism such as the activation of amidoxime prodrugs. However, the endogenous function of the protein is not fully understood. Among other functions, an involvement in lipogenesis is discussed. To study the potential involvement of the protein in energy metabolism, we tested whether the mARC protein and its partners are regulated due to fasting and high fat diet in mice. We used qRT-PCR for expression studies, Western Blot analysis to study protein levels and an N-reductive biotransformation assay to gain activity data. Indeed all proteins of the N-reductive system are regulated by fasting and its activity decreases. To study the potential impact of these changes on prodrug activation in vivo, another mice experiment was conducted. Model compound Benzamidoxime was injected to mice that underwent fasting and the resulting metabolite of the N-reductive reaction, benzamidine, was determined. Albeit altered in vitro activity, no changes in the metabolite concentration in vivo were detectable and we can dispel concerns that fasting alters prodrug activation in animal models. With respect to high fat diet, changes in the mARC proteins occur that result in increased N-reductive activity. With thi
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the n reductive system composed of mitochondrial amidoxime reducing component marc cytochrome b5 cyb5b and cytochrome b5 reductase cyb5r is regulated by fasting and high fat diet in mice
PLOS ONE, 2014Co-Authors: Heyka H. Jakobs, Antje Havemeyer, Michal Mikula, Adriana Strzalkowska, Artur Dzwonek, Marta Gajewska, Ewa E. Hennig, Jerzy Ostrowski, Monika Borowachmielak, Bernd ClementAbstract:The mitochondrial amidoxime reducing component mARC is the fourth mammalian molybdenum enzyme. The protein is capable of reducing N-oxygenated structures, but requires cytochrome b5 and cytochrome b5 reductase for electron transfer to catalyze such reactions. It is well accepted that the enzyme is involved in N-reductive drug metabolism such as the activation of amidoxime prodrugs. However, the endogenous function of the protein is not fully understood. Among other functions, an involvement in lipogenesis is discussed. To study the potential involvement of the protein in energy metabolism, we tested whether the mARC protein and its partners are regulated due to fasting and high fat diet in mice. We used qRT-PCR for expression studies, Western Blot analysis to study protein levels and an N-reductive biotransformation assay to gain activity data. Indeed all proteins of the N-reductive system are regulated by fasting and its activity decreases. To study the potential impact of these changes on prodrug activation in vivo, another mice experiment was conducted. Model compound Benzamidoxime was injected to mice that underwent fasting and the resulting metabolite of the N-reductive reaction, benzamidine, was determined. Albeit altered in vitro activity, no changes in the metabolite concentration in vivo were detectable and we can dispel concerns that fasting alters prodrug activation in animal models. With respect to high fat diet, changes in the mARC proteins occur that result in increased N-reductive activity. With this study we provide further evidence that the endogenous function of the mARC protein is linked with lipid metabolism.
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Scheme of the N-reductive reaction with model compound Benzamidoxime by mARC, CYB5B and CYB5R.
2014Co-Authors: Heyka H. Jakobs, Antje Havemeyer, Michal Mikula, Adriana Strzalkowska, Monika Borowa-chmielak, Artur Dzwonek, Marta Gajewska, Ewa E. Hennig, Jerzy Ostrowski, Bernd ClementAbstract:Electrons are transferred from NADH via FADH in CYB5R, hem in CYB5B and Moco in mARC1/2 to Benzamidoxime, the latter is reduced to benzamidine.
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the fourth molybdenum containing enzyme marc cloning and involvement in the activation of n hydroxylated prodrugs
Journal of Medicinal Chemistry, 2008Co-Authors: Sanja Gruenewald, Florian Bittner, Ralf R. Mendel, Bettina Wahl, Helen Hungeling, Stephanie Kanzow, Joscha Kotthaus, Ulrike Schwering, Bernd ClementAbstract:The recently discovered mammalian molybdoprotein mARC1 is capable of reducing N-hydroxylated compounds. Upon reconstitution with cytochrome b5 and b5 reductase, Benzamidoxime, pentamidine, and diminazene amidoximes, N-hydroxymelagatran, guanoxabenz, and N-hydroxydebrisoquine are efficiently reduced. These substances are amidoxime/N-hydroxyguanidine prodrugs, leading to improved bioavailability compared to the active amidines/guanidines. Thus, the recombinant enzyme allows prediction about in vivo reduction of N-hydroxylated prodrugs. Furthermore, the prodrug principle is not dependent on cytochrome P450 enzymes.
Antje Havemeyer - One of the best experts on this subject based on the ideXlab platform.
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DMD #5249 1
2016Co-Authors: Bernd Clement, Sabine Mau, Stephanie Deters, Antje HavemeyerAbstract:Hepatic, extrahepatic, microsomal, and mitochondrial activation of the N-hydroxylated prodrugs Benzamidoxime, guanoxabenz, and Ro 48-365
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The N-Reductive System Composed of Mitochondrial Amidoxime Reducing Component (mARC), Cytochrome b5 (CYB5B) and Cytochrome b5 Reductase (CYB5R) Is Regulated by Fasting and High Fat Diet in Mice
2016Co-Authors: Heyka H. Jakobs, Antje Havemeyer, Michal Mikula, Adriana Strzalkowska, Artur Dzwonek, Marta Gajewska, Ewa E. Hennig, Jerzy Ostrowski, Monika Borowa, Bernd ClementAbstract:The mitochondrial amidoxime reducing component mARC is the fourth mammalian molybdenum enzyme. The protein is capable of reducing N-oxygenated structures, but requires cytochrome b5 and cytochrome b5 reductase for electron transfer to catalyze such reactions. It is well accepted that the enzyme is involved in N-reductive drug metabolism such as the activation of amidoxime prodrugs. However, the endogenous function of the protein is not fully understood. Among other functions, an involvement in lipogenesis is discussed. To study the potential involvement of the protein in energy metabolism, we tested whether the mARC protein and its partners are regulated due to fasting and high fat diet in mice. We used qRT-PCR for expression studies, Western Blot analysis to study protein levels and an N-reductive biotransformation assay to gain activity data. Indeed all proteins of the N-reductive system are regulated by fasting and its activity decreases. To study the potential impact of these changes on prodrug activation in vivo, another mice experiment was conducted. Model compound Benzamidoxime was injected to mice that underwent fasting and the resulting metabolite of the N-reductive reaction, benzamidine, was determined. Albeit altered in vitro activity, no changes in the metabolite concentration in vivo were detectable and we can dispel concerns that fasting alters prodrug activation in animal models. With respect to high fat diet, changes in the mARC proteins occur that result in increased N-reductive activity. With thi
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the n reductive system composed of mitochondrial amidoxime reducing component marc cytochrome b5 cyb5b and cytochrome b5 reductase cyb5r is regulated by fasting and high fat diet in mice
PLOS ONE, 2014Co-Authors: Heyka H. Jakobs, Antje Havemeyer, Michal Mikula, Adriana Strzalkowska, Artur Dzwonek, Marta Gajewska, Ewa E. Hennig, Jerzy Ostrowski, Monika Borowachmielak, Bernd ClementAbstract:The mitochondrial amidoxime reducing component mARC is the fourth mammalian molybdenum enzyme. The protein is capable of reducing N-oxygenated structures, but requires cytochrome b5 and cytochrome b5 reductase for electron transfer to catalyze such reactions. It is well accepted that the enzyme is involved in N-reductive drug metabolism such as the activation of amidoxime prodrugs. However, the endogenous function of the protein is not fully understood. Among other functions, an involvement in lipogenesis is discussed. To study the potential involvement of the protein in energy metabolism, we tested whether the mARC protein and its partners are regulated due to fasting and high fat diet in mice. We used qRT-PCR for expression studies, Western Blot analysis to study protein levels and an N-reductive biotransformation assay to gain activity data. Indeed all proteins of the N-reductive system are regulated by fasting and its activity decreases. To study the potential impact of these changes on prodrug activation in vivo, another mice experiment was conducted. Model compound Benzamidoxime was injected to mice that underwent fasting and the resulting metabolite of the N-reductive reaction, benzamidine, was determined. Albeit altered in vitro activity, no changes in the metabolite concentration in vivo were detectable and we can dispel concerns that fasting alters prodrug activation in animal models. With respect to high fat diet, changes in the mARC proteins occur that result in increased N-reductive activity. With this study we provide further evidence that the endogenous function of the mARC protein is linked with lipid metabolism.
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Scheme of the N-reductive reaction with model compound Benzamidoxime by mARC, CYB5B and CYB5R.
2014Co-Authors: Heyka H. Jakobs, Antje Havemeyer, Michal Mikula, Adriana Strzalkowska, Monika Borowa-chmielak, Artur Dzwonek, Marta Gajewska, Ewa E. Hennig, Jerzy Ostrowski, Bernd ClementAbstract:Electrons are transferred from NADH via FADH in CYB5R, hem in CYB5B and Moco in mARC1/2 to Benzamidoxime, the latter is reduced to benzamidine.
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Identification of the Missing Component in the Mitochondrial Benzamidoxime Prodrug-converting System as a Novel Molybdenum Enzyme
Journal of Biological Chemistry, 2006Co-Authors: Antje Havemeyer, Florian Bittner, Silke Wollers, Ralf R. Mendel, Thomas Kunze, Bernd ClementAbstract:Abstract Amidoximes can be used as prodrugs for amidines and related functional groups to enhance their intestinal absorption. These prodrugs are reduced to their active amidines. Other N-hydroxylated structures are mutagenic or responsible for toxic effects of drugs and are detoxified by reduction. In this study, a N-reductive enzyme system of pig liver mitochondria using Benzamidoxime as a model substrate was identified. A protein fraction free from cytochrome b5 and cytochrome b5 reductase was purified, enhancing 250-fold the minor Benzamidoxime-reductase activity catalyzed by the membrane-bound cytochrome b5/NADH cytochrome b5 reductase system. This fraction contained a 35-kDa protein with homologies to the C-terminal domain of the human molybdenum cofactor sulfurase. Here it was demonstrated that this 35-kDa protein contains molybdenum cofactor and forms the hitherto ill defined third component of the N-reductive complex in the outer mitochondrial membrane. Thus, the 35-kDa protein represents a novel group of molybdenum proteins in eukaryotes as it forms the catalytic part of a three-component enzyme complex consisting of separate proteins. Supporting these findings, recombinant C-terminal domain of the human molybdenum cofactor sulfurase exhibited N-reductive activity in vitro, which was strictly dependent on molybdenum cofactor.
Heyka H. Jakobs - One of the best experts on this subject based on the ideXlab platform.
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The N-Reductive System Composed of Mitochondrial Amidoxime Reducing Component (mARC), Cytochrome b5 (CYB5B) and Cytochrome b5 Reductase (CYB5R) Is Regulated by Fasting and High Fat Diet in Mice
2016Co-Authors: Heyka H. Jakobs, Antje Havemeyer, Michal Mikula, Adriana Strzalkowska, Artur Dzwonek, Marta Gajewska, Ewa E. Hennig, Jerzy Ostrowski, Monika Borowa, Bernd ClementAbstract:The mitochondrial amidoxime reducing component mARC is the fourth mammalian molybdenum enzyme. The protein is capable of reducing N-oxygenated structures, but requires cytochrome b5 and cytochrome b5 reductase for electron transfer to catalyze such reactions. It is well accepted that the enzyme is involved in N-reductive drug metabolism such as the activation of amidoxime prodrugs. However, the endogenous function of the protein is not fully understood. Among other functions, an involvement in lipogenesis is discussed. To study the potential involvement of the protein in energy metabolism, we tested whether the mARC protein and its partners are regulated due to fasting and high fat diet in mice. We used qRT-PCR for expression studies, Western Blot analysis to study protein levels and an N-reductive biotransformation assay to gain activity data. Indeed all proteins of the N-reductive system are regulated by fasting and its activity decreases. To study the potential impact of these changes on prodrug activation in vivo, another mice experiment was conducted. Model compound Benzamidoxime was injected to mice that underwent fasting and the resulting metabolite of the N-reductive reaction, benzamidine, was determined. Albeit altered in vitro activity, no changes in the metabolite concentration in vivo were detectable and we can dispel concerns that fasting alters prodrug activation in animal models. With respect to high fat diet, changes in the mARC proteins occur that result in increased N-reductive activity. With thi
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the n reductive system composed of mitochondrial amidoxime reducing component marc cytochrome b5 cyb5b and cytochrome b5 reductase cyb5r is regulated by fasting and high fat diet in mice
PLOS ONE, 2014Co-Authors: Heyka H. Jakobs, Antje Havemeyer, Michal Mikula, Adriana Strzalkowska, Artur Dzwonek, Marta Gajewska, Ewa E. Hennig, Jerzy Ostrowski, Monika Borowachmielak, Bernd ClementAbstract:The mitochondrial amidoxime reducing component mARC is the fourth mammalian molybdenum enzyme. The protein is capable of reducing N-oxygenated structures, but requires cytochrome b5 and cytochrome b5 reductase for electron transfer to catalyze such reactions. It is well accepted that the enzyme is involved in N-reductive drug metabolism such as the activation of amidoxime prodrugs. However, the endogenous function of the protein is not fully understood. Among other functions, an involvement in lipogenesis is discussed. To study the potential involvement of the protein in energy metabolism, we tested whether the mARC protein and its partners are regulated due to fasting and high fat diet in mice. We used qRT-PCR for expression studies, Western Blot analysis to study protein levels and an N-reductive biotransformation assay to gain activity data. Indeed all proteins of the N-reductive system are regulated by fasting and its activity decreases. To study the potential impact of these changes on prodrug activation in vivo, another mice experiment was conducted. Model compound Benzamidoxime was injected to mice that underwent fasting and the resulting metabolite of the N-reductive reaction, benzamidine, was determined. Albeit altered in vitro activity, no changes in the metabolite concentration in vivo were detectable and we can dispel concerns that fasting alters prodrug activation in animal models. With respect to high fat diet, changes in the mARC proteins occur that result in increased N-reductive activity. With this study we provide further evidence that the endogenous function of the mARC protein is linked with lipid metabolism.
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Scheme of the N-reductive reaction with model compound Benzamidoxime by mARC, CYB5B and CYB5R.
2014Co-Authors: Heyka H. Jakobs, Antje Havemeyer, Michal Mikula, Adriana Strzalkowska, Monika Borowa-chmielak, Artur Dzwonek, Marta Gajewska, Ewa E. Hennig, Jerzy Ostrowski, Bernd ClementAbstract:Electrons are transferred from NADH via FADH in CYB5R, hem in CYB5B and Moco in mARC1/2 to Benzamidoxime, the latter is reduced to benzamidine.
Lauren A Trepanier - One of the best experts on this subject based on the ideXlab platform.
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nadh cytochrome b5 reductase and cytochrome b5 catalyze the microsomal reduction of xenobiotic hydroxylamines and amidoximes in humans
Journal of Pharmacology and Experimental Therapeutics, 2004Co-Authors: Joseph R Kurian, Sunil U Bajad, Jackie L Miller, Nathaniel A Chin, Lauren A TrepanierAbstract: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.
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Nadh cytochrome b5 reductase and cytochrome b5 catalyze the microsomal reduction of xenobiotic hydroxylamines and amidoximes in humans
2004Co-Authors: Joseph R Kurian, Sunil U Bajad, Jackie L Miller, Nathaniel A Chin, Lauren A TrepanierAbstract: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 sys-tem. We hypothesized that NADH cytochrome b5 reductase and cytochrome b5 were responsible for this enzymatic activity in humans. Purified human soluble NADH cytochrome b5 re-ductase and cytochrome b5, expressed in Escherichia coli, efficiently catalyzed the reduction of sulfamethoxazole hydrox-ylamine, dapsone hydroxylamine, and Benzamidoxime, with apparent Km values similar to those found in human liver mi-crosomes and specific activities (Vmax) 74 to 235 times higher than in microsomes. Minimal activity was seen with either pro-tein alone, and microsomal protein did not enhance activit
Michal Mikula - One of the best experts on this subject based on the ideXlab platform.
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The N-Reductive System Composed of Mitochondrial Amidoxime Reducing Component (mARC), Cytochrome b5 (CYB5B) and Cytochrome b5 Reductase (CYB5R) Is Regulated by Fasting and High Fat Diet in Mice
2016Co-Authors: Heyka H. Jakobs, Antje Havemeyer, Michal Mikula, Adriana Strzalkowska, Artur Dzwonek, Marta Gajewska, Ewa E. Hennig, Jerzy Ostrowski, Monika Borowa, Bernd ClementAbstract:The mitochondrial amidoxime reducing component mARC is the fourth mammalian molybdenum enzyme. The protein is capable of reducing N-oxygenated structures, but requires cytochrome b5 and cytochrome b5 reductase for electron transfer to catalyze such reactions. It is well accepted that the enzyme is involved in N-reductive drug metabolism such as the activation of amidoxime prodrugs. However, the endogenous function of the protein is not fully understood. Among other functions, an involvement in lipogenesis is discussed. To study the potential involvement of the protein in energy metabolism, we tested whether the mARC protein and its partners are regulated due to fasting and high fat diet in mice. We used qRT-PCR for expression studies, Western Blot analysis to study protein levels and an N-reductive biotransformation assay to gain activity data. Indeed all proteins of the N-reductive system are regulated by fasting and its activity decreases. To study the potential impact of these changes on prodrug activation in vivo, another mice experiment was conducted. Model compound Benzamidoxime was injected to mice that underwent fasting and the resulting metabolite of the N-reductive reaction, benzamidine, was determined. Albeit altered in vitro activity, no changes in the metabolite concentration in vivo were detectable and we can dispel concerns that fasting alters prodrug activation in animal models. With respect to high fat diet, changes in the mARC proteins occur that result in increased N-reductive activity. With thi
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the n reductive system composed of mitochondrial amidoxime reducing component marc cytochrome b5 cyb5b and cytochrome b5 reductase cyb5r is regulated by fasting and high fat diet in mice
PLOS ONE, 2014Co-Authors: Heyka H. Jakobs, Antje Havemeyer, Michal Mikula, Adriana Strzalkowska, Artur Dzwonek, Marta Gajewska, Ewa E. Hennig, Jerzy Ostrowski, Monika Borowachmielak, Bernd ClementAbstract:The mitochondrial amidoxime reducing component mARC is the fourth mammalian molybdenum enzyme. The protein is capable of reducing N-oxygenated structures, but requires cytochrome b5 and cytochrome b5 reductase for electron transfer to catalyze such reactions. It is well accepted that the enzyme is involved in N-reductive drug metabolism such as the activation of amidoxime prodrugs. However, the endogenous function of the protein is not fully understood. Among other functions, an involvement in lipogenesis is discussed. To study the potential involvement of the protein in energy metabolism, we tested whether the mARC protein and its partners are regulated due to fasting and high fat diet in mice. We used qRT-PCR for expression studies, Western Blot analysis to study protein levels and an N-reductive biotransformation assay to gain activity data. Indeed all proteins of the N-reductive system are regulated by fasting and its activity decreases. To study the potential impact of these changes on prodrug activation in vivo, another mice experiment was conducted. Model compound Benzamidoxime was injected to mice that underwent fasting and the resulting metabolite of the N-reductive reaction, benzamidine, was determined. Albeit altered in vitro activity, no changes in the metabolite concentration in vivo were detectable and we can dispel concerns that fasting alters prodrug activation in animal models. With respect to high fat diet, changes in the mARC proteins occur that result in increased N-reductive activity. With this study we provide further evidence that the endogenous function of the mARC protein is linked with lipid metabolism.
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Scheme of the N-reductive reaction with model compound Benzamidoxime by mARC, CYB5B and CYB5R.
2014Co-Authors: Heyka H. Jakobs, Antje Havemeyer, Michal Mikula, Adriana Strzalkowska, Monika Borowa-chmielak, Artur Dzwonek, Marta Gajewska, Ewa E. Hennig, Jerzy Ostrowski, Bernd ClementAbstract:Electrons are transferred from NADH via FADH in CYB5R, hem in CYB5B and Moco in mARC1/2 to Benzamidoxime, the latter is reduced to benzamidine.