The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Hung-wen Liu - One of the best experts on this subject based on the ideXlab platform.
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biosynthesis of oxetanocin a includes a b12 dependent radical sam enzyme that can catalyze both oxidative ring contraction and the demethylation of sam
Biochemistry, 2021Co-Authors: Aoshu Zhong, Yung Nan Liu, Yuhsuan Lee, Hung-wen LiuAbstract:Oxetanocin-A is an antitumor, antiviral, and antibacterial nucleoside. It is biosynthesized via the oxidative ring contraction of a purine nucleoside co-opted from primary metabolism. This reaction is catalyzed by a B12-dependent radical S-adenosyl-l-methionine (SAM) enzyme, OxsB, and a phosphohydrolase, OxsA. Previous experiments showed that the product of the OxsB/OxsA-catalyzed reaction is an oxetane aldehyde produced alongside an uncharacterized byproduct. Experiments reported herein reveal that OxsB/OxsA complex formation is crucial for the ring contraction reaction and that reduction of the aldehyde intermediate is catalyzed by a nonspecific dehydrogenase from the general cellular pool. In addition, the byproduct is identified as a 1,3-thiazinane adduct between the aldehyde and l-homocysteine. While homocysteine was never included in the OxsB/OxsA assays, the data suggest that it can be generated from SAM via S-Adenosyl-L-Homocysteine (SAH). Further study revealed that conversion of SAM to SAH is facilitated by OxsB; however, the subsequent conversion of SAH to homocysteine is due to protein contaminants that co-purify with OxsA. Nevertheless, the observed demethylation of SAM to SAH suggests possible methyltransferase activity of OxsB, and substrate methylation was indeed detected in the OxsB-catalyzed reaction. This work is significant because it not only completes the description of the oxetanocin-A biosynthetic pathway but also suggests that OxsB may be capable of methyltransferase activity.
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genk catalyzed c 6 methylation in the biosynthesis of gentamicin isolation and characterization of a cobalamin dependent radical sam enzyme
Journal of the American Chemical Society, 2013Co-Authors: Hak Joong Kim, Yasushi Ogasawara, Reid M Mccarty, Yung Nan Liu, Steven O Mansoorabadi, Jake Levieux, Hung-wen LiuAbstract:The existence of cobalamin (Cbl)-dependent enzymes that are members of the radical S-adenosyl-l-methionine (SAM) superfamily was previously predicted on the basis of bioinformatic analysis. A number of these are Cbl-dependent methyltransferases, but the details surrounding their reaction mechanisms have remained unclear. In this report we demonstrate the in vitro activity of GenK, a Cbl-dependent radical SAM enzyme that methylates an unactivated sp(3) carbon during the biosynthesis of gentamicin, an aminoglycoside antibiotic. Experiments to investigate the stoichiometry of the GenK reaction revealed that 1 equiv each of 5'-deoxyadenosine and S-adenosyl-homocysteine are produced for each methylation reaction catalyzed by GenK. Furthermore, isotope-labeling experiments demonstrate that the S-methyl group from SAM is transferred to Cbl and the aminoglycoside product during the course of the reaction. On the basis of these results, one mechanistic possibility for the GenK reaction can be ruled out, and further questions regarding the mechanisms of Cbl-dependent radical SAM methyltransferases, in general, are discussed.
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genk catalyzed c 6 methylation in the biosynthesis of gentamicin isolation and characterization of a cobalamin dependent radical sam enzyme
Journal of the American Chemical Society, 2013Co-Authors: Hak Joong Kim, Yasushi Ogasawara, Reid M Mccarty, Yung Nan Liu, Steven O Mansoorabadi, Jake Levieux, Hung-wen LiuAbstract:The existence of cobalamin (Cbl)-dependent enzymes that are members of the radical S-adenosyl-l-methionine (SAM) superfamily was previously predicted on the basis of bioinformatic analysis. A number of these are Cbl-dependent methyltransferases, but the details surrounding their reaction mechanisms have remained unclear. In this report we demonstrate the in vitro activity of GenK, a Cbl-dependent radical SAM enzyme that methylates an unactivated sp3 carbon during the biosynthesis of gentamicin, an aminoglycoside antibiotic. Experiments to investigate the stoichiometry of the GenK reaction revealed that 1 equiv each of 5′-deoxyadenosine and S-adenosyl-homocysteine are produced for each methylation reaction catalyzed by GenK. Furthermore, isotope-labeling experiments demonstrate that the S-methyl group from SAM is transferred to Cbl and the aminoglycoside product during the course of the reaction. On the basis of these results, one mechanistic possibility for the GenK reaction can be ruled out, and further ...
Steven O Mansoorabadi - One of the best experts on this subject based on the ideXlab platform.
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genk catalyzed c 6 methylation in the biosynthesis of gentamicin isolation and characterization of a cobalamin dependent radical sam enzyme
Journal of the American Chemical Society, 2013Co-Authors: Hak Joong Kim, Yasushi Ogasawara, Reid M Mccarty, Yung Nan Liu, Steven O Mansoorabadi, Jake Levieux, Hung-wen LiuAbstract:The existence of cobalamin (Cbl)-dependent enzymes that are members of the radical S-adenosyl-l-methionine (SAM) superfamily was previously predicted on the basis of bioinformatic analysis. A number of these are Cbl-dependent methyltransferases, but the details surrounding their reaction mechanisms have remained unclear. In this report we demonstrate the in vitro activity of GenK, a Cbl-dependent radical SAM enzyme that methylates an unactivated sp(3) carbon during the biosynthesis of gentamicin, an aminoglycoside antibiotic. Experiments to investigate the stoichiometry of the GenK reaction revealed that 1 equiv each of 5'-deoxyadenosine and S-adenosyl-homocysteine are produced for each methylation reaction catalyzed by GenK. Furthermore, isotope-labeling experiments demonstrate that the S-methyl group from SAM is transferred to Cbl and the aminoglycoside product during the course of the reaction. On the basis of these results, one mechanistic possibility for the GenK reaction can be ruled out, and further questions regarding the mechanisms of Cbl-dependent radical SAM methyltransferases, in general, are discussed.
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genk catalyzed c 6 methylation in the biosynthesis of gentamicin isolation and characterization of a cobalamin dependent radical sam enzyme
Journal of the American Chemical Society, 2013Co-Authors: Hak Joong Kim, Yasushi Ogasawara, Reid M Mccarty, Yung Nan Liu, Steven O Mansoorabadi, Jake Levieux, Hung-wen LiuAbstract:The existence of cobalamin (Cbl)-dependent enzymes that are members of the radical S-adenosyl-l-methionine (SAM) superfamily was previously predicted on the basis of bioinformatic analysis. A number of these are Cbl-dependent methyltransferases, but the details surrounding their reaction mechanisms have remained unclear. In this report we demonstrate the in vitro activity of GenK, a Cbl-dependent radical SAM enzyme that methylates an unactivated sp3 carbon during the biosynthesis of gentamicin, an aminoglycoside antibiotic. Experiments to investigate the stoichiometry of the GenK reaction revealed that 1 equiv each of 5′-deoxyadenosine and S-adenosyl-homocysteine are produced for each methylation reaction catalyzed by GenK. Furthermore, isotope-labeling experiments demonstrate that the S-methyl group from SAM is transferred to Cbl and the aminoglycoside product during the course of the reaction. On the basis of these results, one mechanistic possibility for the GenK reaction can be ruled out, and further ...
Yung Nan Liu - One of the best experts on this subject based on the ideXlab platform.
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biosynthesis of oxetanocin a includes a b12 dependent radical sam enzyme that can catalyze both oxidative ring contraction and the demethylation of sam
Biochemistry, 2021Co-Authors: Aoshu Zhong, Yung Nan Liu, Yuhsuan Lee, Hung-wen LiuAbstract:Oxetanocin-A is an antitumor, antiviral, and antibacterial nucleoside. It is biosynthesized via the oxidative ring contraction of a purine nucleoside co-opted from primary metabolism. This reaction is catalyzed by a B12-dependent radical S-adenosyl-l-methionine (SAM) enzyme, OxsB, and a phosphohydrolase, OxsA. Previous experiments showed that the product of the OxsB/OxsA-catalyzed reaction is an oxetane aldehyde produced alongside an uncharacterized byproduct. Experiments reported herein reveal that OxsB/OxsA complex formation is crucial for the ring contraction reaction and that reduction of the aldehyde intermediate is catalyzed by a nonspecific dehydrogenase from the general cellular pool. In addition, the byproduct is identified as a 1,3-thiazinane adduct between the aldehyde and l-homocysteine. While homocysteine was never included in the OxsB/OxsA assays, the data suggest that it can be generated from SAM via S-Adenosyl-L-Homocysteine (SAH). Further study revealed that conversion of SAM to SAH is facilitated by OxsB; however, the subsequent conversion of SAH to homocysteine is due to protein contaminants that co-purify with OxsA. Nevertheless, the observed demethylation of SAM to SAH suggests possible methyltransferase activity of OxsB, and substrate methylation was indeed detected in the OxsB-catalyzed reaction. This work is significant because it not only completes the description of the oxetanocin-A biosynthetic pathway but also suggests that OxsB may be capable of methyltransferase activity.
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genk catalyzed c 6 methylation in the biosynthesis of gentamicin isolation and characterization of a cobalamin dependent radical sam enzyme
Journal of the American Chemical Society, 2013Co-Authors: Hak Joong Kim, Yasushi Ogasawara, Reid M Mccarty, Yung Nan Liu, Steven O Mansoorabadi, Jake Levieux, Hung-wen LiuAbstract:The existence of cobalamin (Cbl)-dependent enzymes that are members of the radical S-adenosyl-l-methionine (SAM) superfamily was previously predicted on the basis of bioinformatic analysis. A number of these are Cbl-dependent methyltransferases, but the details surrounding their reaction mechanisms have remained unclear. In this report we demonstrate the in vitro activity of GenK, a Cbl-dependent radical SAM enzyme that methylates an unactivated sp(3) carbon during the biosynthesis of gentamicin, an aminoglycoside antibiotic. Experiments to investigate the stoichiometry of the GenK reaction revealed that 1 equiv each of 5'-deoxyadenosine and S-adenosyl-homocysteine are produced for each methylation reaction catalyzed by GenK. Furthermore, isotope-labeling experiments demonstrate that the S-methyl group from SAM is transferred to Cbl and the aminoglycoside product during the course of the reaction. On the basis of these results, one mechanistic possibility for the GenK reaction can be ruled out, and further questions regarding the mechanisms of Cbl-dependent radical SAM methyltransferases, in general, are discussed.
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genk catalyzed c 6 methylation in the biosynthesis of gentamicin isolation and characterization of a cobalamin dependent radical sam enzyme
Journal of the American Chemical Society, 2013Co-Authors: Hak Joong Kim, Yasushi Ogasawara, Reid M Mccarty, Yung Nan Liu, Steven O Mansoorabadi, Jake Levieux, Hung-wen LiuAbstract:The existence of cobalamin (Cbl)-dependent enzymes that are members of the radical S-adenosyl-l-methionine (SAM) superfamily was previously predicted on the basis of bioinformatic analysis. A number of these are Cbl-dependent methyltransferases, but the details surrounding their reaction mechanisms have remained unclear. In this report we demonstrate the in vitro activity of GenK, a Cbl-dependent radical SAM enzyme that methylates an unactivated sp3 carbon during the biosynthesis of gentamicin, an aminoglycoside antibiotic. Experiments to investigate the stoichiometry of the GenK reaction revealed that 1 equiv each of 5′-deoxyadenosine and S-adenosyl-homocysteine are produced for each methylation reaction catalyzed by GenK. Furthermore, isotope-labeling experiments demonstrate that the S-methyl group from SAM is transferred to Cbl and the aminoglycoside product during the course of the reaction. On the basis of these results, one mechanistic possibility for the GenK reaction can be ruled out, and further ...
Hak Joong Kim - One of the best experts on this subject based on the ideXlab platform.
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genk catalyzed c 6 methylation in the biosynthesis of gentamicin isolation and characterization of a cobalamin dependent radical sam enzyme
Journal of the American Chemical Society, 2013Co-Authors: Hak Joong Kim, Yasushi Ogasawara, Reid M Mccarty, Yung Nan Liu, Steven O Mansoorabadi, Jake Levieux, Hung-wen LiuAbstract:The existence of cobalamin (Cbl)-dependent enzymes that are members of the radical S-adenosyl-l-methionine (SAM) superfamily was previously predicted on the basis of bioinformatic analysis. A number of these are Cbl-dependent methyltransferases, but the details surrounding their reaction mechanisms have remained unclear. In this report we demonstrate the in vitro activity of GenK, a Cbl-dependent radical SAM enzyme that methylates an unactivated sp(3) carbon during the biosynthesis of gentamicin, an aminoglycoside antibiotic. Experiments to investigate the stoichiometry of the GenK reaction revealed that 1 equiv each of 5'-deoxyadenosine and S-adenosyl-homocysteine are produced for each methylation reaction catalyzed by GenK. Furthermore, isotope-labeling experiments demonstrate that the S-methyl group from SAM is transferred to Cbl and the aminoglycoside product during the course of the reaction. On the basis of these results, one mechanistic possibility for the GenK reaction can be ruled out, and further questions regarding the mechanisms of Cbl-dependent radical SAM methyltransferases, in general, are discussed.
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genk catalyzed c 6 methylation in the biosynthesis of gentamicin isolation and characterization of a cobalamin dependent radical sam enzyme
Journal of the American Chemical Society, 2013Co-Authors: Hak Joong Kim, Yasushi Ogasawara, Reid M Mccarty, Yung Nan Liu, Steven O Mansoorabadi, Jake Levieux, Hung-wen LiuAbstract:The existence of cobalamin (Cbl)-dependent enzymes that are members of the radical S-adenosyl-l-methionine (SAM) superfamily was previously predicted on the basis of bioinformatic analysis. A number of these are Cbl-dependent methyltransferases, but the details surrounding their reaction mechanisms have remained unclear. In this report we demonstrate the in vitro activity of GenK, a Cbl-dependent radical SAM enzyme that methylates an unactivated sp3 carbon during the biosynthesis of gentamicin, an aminoglycoside antibiotic. Experiments to investigate the stoichiometry of the GenK reaction revealed that 1 equiv each of 5′-deoxyadenosine and S-adenosyl-homocysteine are produced for each methylation reaction catalyzed by GenK. Furthermore, isotope-labeling experiments demonstrate that the S-methyl group from SAM is transferred to Cbl and the aminoglycoside product during the course of the reaction. On the basis of these results, one mechanistic possibility for the GenK reaction can be ruled out, and further ...
Robert J Almassy - One of the best experts on this subject based on the ideXlab platform.
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structure based design synthesis and antimicrobial activity of purine derived sah mta nucleosidase inhibitors
Bioorganic & Medicinal Chemistry Letters, 2004Co-Authors: Martina E Tedder, Zhe Nie, Stephen Margosiak, Shaosong Chu, Victoria Feher, Robert J Almassy, Krzysztof Appelt, Kraig M YagerAbstract:The structure-based design, synthesis, and biological activity of novel inhibitors of S-adenosyl homocysteine/methylthioadenosine (SAH/MTA) nucleosidase are described. Using 6-substituted purine and deaza purines as the core scaffolds, a systematic and structure guided series of modifications provided low nM inhibitors with broad-spectrum antimicrobial activity.
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structure based design synthesis and antimicrobial activity of indazole derived sah mta nucleosidase inhibitors
Journal of Medicinal Chemistry, 2003Co-Authors: Sam Chu, Martina E Tedder, Zhe Nie, Stephen Margosiak, Victoria A Feher, Mitra Khalili, Victor I Nikulin, James Levin, Kelly G Sprankle, Robert J AlmassyAbstract:The structure-based design, synthesis, and biological activity of a novel indazole-containing inhibitor series for S-adenosyl homocysteine/methylthioadenosine (SAH/MTA) nucleosidase are described. Use of 5-aminoindazole as the core scaffold provided a structure-guided series of low nanomolar inhibitors with broad-spectrum antimicrobial activity. The implementation of structure-based methodologies provided a 6000-fold increase in potency over a short timeline (several months) and an economy of synthesized compounds.
