Reaction Of Hydrogen Abstraction
Mostrando 13-24 de 25 artigos, teses e dissertações.
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13. Liver microsomal cytochrome P-450 and the oxidative metabolism of arachidonic acid.
Arachidonic acid is oxidatively metabolized by rat liver microsomes at a rate of approximately 5 nmol per min per mg of protein at 25 degrees C. This reaction is dependent on the presence of NADPH and oxygen. Studies with various inhibitors indicate a role for membrane-bound cytochrome P-450 in the transformation of arachidonic acid to a mixture of hydroxy a
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14. A single active site residue directs oxygenation stereospecificity in lipoxygenases: Stereocontrol is linked to the position of oxygenation
Lipoxygenases are a class of dioxygenases that form hydroperoxy fatty acids with distinct positional and stereo configurations. Several amino acid residues influencing regiospecificity have been identified, whereas the basis of stereocontrol is not understood. We have now identified a single residue in the lipoxygenase catalytic domain that is important for
National Academy of Sciences.
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15. Manganese(II)-bicarbonate-mediated catalytic activity for hydrogen peroxide dismutation and amino acid oxidation: detection of free radical intermediates.
To examine the structural identities of reactive free radicals and the mechanism of the oxidative modification of proteins, we used EPR and spin-trapping methods to investigate the oxidation of amino acids by H2O2 as well as the decomposition of H2O2 itself catalyzed by Mn(II) ions. Superoxide and hydroxyl radicals (O2-. and OH.) were trapped by a spin trap,
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16. Mechanisms of DNA damage by chromium(V) carcinogens.
Reactions of bis(2-ethyl-2-hydroxy-butanato)oxochromate(V) with pUC19 DNA, single-stranded calf thymus DNA (ss-ctDNA), a synthetic oligonucleotide, 5'-GATCTATGGACTTACTTCAAGGCCGGGTAATGCTA-3' (35mer), deoxyguanosine and guanine were carried out in Bis-Tris buffer at pH 7.0. The plasmid DNA was only nicked, whereas the single-stranded DNA suffered extensive dam
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17. Protonation of the β-lactam nitrogen is the trigger event in the catalytic action of class A β-lactamases
The pH dependence of the pKa values of all ionizable groups and of the electrostatic potential at grid points corresponding to catalytically important atoms in the active site of TEM-1 β-lactamase has been calculated by a mean-field approach for reaction intermediates modeled on the basis of energy minimized x-ray crystallographic coordinates. By estimating
The National Academy of Sciences.
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18. Structural origins of efficient proton abstraction from carbon by a catalytic antibody
Antibody 34E4 catalyzes the conversion of benzisoxazoles to salicylonitriles with high rates and multiple turnovers. The crystal structure of its complex with the benzimidazolium hapten at 2.5-Å resolution shows that a combination of hydrogen bonding, π stacking, and van der Waals interactions is exploited to position both the base, GluH50, and the substra
National Academy of Sciences.
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19. 3'-Formyl phosphate-ended DNA: high-energy intermediate in antibiotic-induced DNA sugar damage.
Under anaerobic conditions where the nitroaromatic radiation-sensitizer misonidazole substitutes for dioxygen, DNA strand breakage (gaps with phosphate residues at each end) by the nonprotein chromophore of the antitumor antibiotic neocarzinostatin (NCS-Chrom) is associated with the generation of a reactive form of formate from the C-5' of deoxyribose of thy
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20. Rapid polyether cleavage via extracellular one-electron oxidation by a brown-rot basidiomycete
Fungi that cause brown rot of wood are essential biomass recyclers and also the principal agents of decay in wooden structures, but the extracellular mechanisms by which they degrade lignocellulose remain unknown. To test the hypothesis that brown-rot fungi use extracellular free radical oxidants as biodegradative tools, Gloeophyllum trabeum was examined for
The National Academy of Sciences.
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21. Aryl-alcohol Oxidase Involved in Lignin Degradation: A MECHANISTIC STUDY BASED ON STEADY AND PRE-STEADY STATE KINETICS AND PRIMARY AND SOLVENT ISOTOPE EFFECTS WITH TWO ALCOHOL SUBSTRATES*
Aryl-alcohol oxidase (AAO) is a FAD-containing enzyme in the GMC (glucose-methanol-choline oxidase) family of oxidoreductases. AAO participates in fungal degradation of lignin, a process of high ecological and biotechnological relevance, by providing the hydrogen peroxide required by ligninolytic peroxidases. In the Pleurotus species, this peroxide is genera
American Society for Biochemistry and Molecular Biology.
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22. Evidence for an Ionic Intermediate in the Transformation of Fatty Acid Hydroperoxide by a Catalase-related Allene Oxide Synthase from the Cyanobacterium Acaryochloris marina*
Allene oxides are reactive epoxides biosynthesized from fatty acid hydroperoxides by specialized cytochrome P450s or by catalase-related hemoproteins. Here we cloned, expressed, and characterized a gene encoding a lipoxygenase-catalase/peroxidase fusion protein from Acaryochloris marina. We identified novel allene oxide synthase (AOS) activity and a by-produ
American Society for Biochemistry and Molecular Biology.
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23. Oxidative Cleavage of Diverse Ethers by an Extracellular Fungal Peroxygenase*
Many litter-decay fungi secrete heme-thiolate peroxygenases that oxidize various organic chemicals, but little is known about the role or mechanism of these enzymes. We found that the extracellular peroxygenase of Agrocybe aegerita catalyzed the H2O2-dependent cleavage of environmentally significant ethers, including methyl t-butyl ether, tetrahydrofuran, an
American Society for Biochemistry and Molecular Biology.
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24. Ras-catalyzed hydrolysis of GTP: a new perspective from model studies.
Despite the biological and medical importance of signal transduction via Ras proteins and despite considerable kinetic and structural studies of wild-type and mutant Ras proteins, the mechanism of Ras-catalyzed GTP hydrolysis remains controversial. We take a different approach to this problem: the uncatalyzed hydrolysis of GTP is analyzed, and the understand