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Oxidative Decarboxylation (oxidative + decarboxylation)
Selected AbstractsChemInform Abstract: Efficient Biomimetic Oxidative Decarboxylation of Some Carboxylic Acids Catalyzed by a Manganese(III) Schiff Base Complex.CHEMINFORM, Issue 51 2009Masoud Nasr-Esfahani Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Catalytic Oxidative Decarboxylation of Some Benzylcarboxylic Acid Derivatives by a New Iron(III) Schiff Base Complex.CHEMINFORM, Issue 39 2009Morteza Montazerozohori Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Conversion of N-Acyl Amino Acids into Imides via Oxidative Decarboxylation Induced by Ag+/Cu2+/S2O82- in Water.CHEMINFORM, Issue 37 2008Wenhua Huang Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Role of a highly conserved YPITP motif in 2-oxoacid:ferredoxin oxidoreductase.,FEBS JOURNAL, Issue 21 2001Heterologous expression of the gene from Sulfolobus sp. strain , characterization of the recombinant, variant enzymes 2-Oxoacid:ferredoxin oxidoreductase from Sulfolobus sp. strain 7, an aerobic and thermoacidophilic crenoarchaeon, catalyses the coenzyme A-dependent oxidative decarboxylation of pyruvate and 2-oxoglutarate, a cognate Zn-7Fe-ferredoxin serving as an electron acceptor. It comprises two subunits, a (632 amino acids) and b (305 amino acids). To further elucidate its structure and function, we constructed a gene expression system. The wild-type recombinant enzyme was indistinguishable from the natural one in every criterion investigated. A series of variants was constructed to elucidate the role of the YPITP-motif (residues 253,257) in subunit a, which is conserved universally in the 2-oxoacid:ferredoxin oxidoreductase (OFOR) family. Single amino-acid replacements at Y253 and P257 by other amino acids caused a drastic loss of enzyme activity. T256, the hydroxyl group of which has been proposed to be essential for binding of the 2-oxo group of the substrate in the Desulfovibrio africanus enzyme, was unexpectedly replaceable with Ala, the kcat and Km for 2-oxoglutarate being ,,33% and ,,51%, respectively, as compared with that of the wild-type enzyme. Replacement at other positions resulted in a significant decrease in the kcat of the reaction while the Km for 2-oxoacid was only slightly affected. Thus, the YPITP-motif is essential for the turnover of the reaction rather than the affinity toward 2-oxoacid. [source] Site-directed mutagenesis of the active site serine290 in flavanone 3,-hydroxylase from Petunia hybridaFEBS JOURNAL, Issue 3 2000Richard Luka Flavanone 3,-hydroxylase (FHT) catalyzes a pivotal reaction in the formation of flavonoids, catechins, proanthocyanidins and anthocyanidins. In the presence of oxygen and ferrous ions the enzyme couples the oxidative decarboxylation of 2-oxoglutarate, releasing carbon dioxide and succinate, with the oxidation of flavanones to produce dihydroflavonols. The hydroxylase had been cloned from Petunia hybrida and expressed in Escherichia coli, and a rapid isolation method for the highly active, recombinant enzyme had been developed. Sequence alignments of the Petunia hydroxylase with various hydroxylating 2-oxoglutarate-dependent dioxygenases revealed few conserved amino acids, including a strictly conserved serine residue (Ser290). This serine was mutated to threonine, alanine or valine, which represent amino acids found at the corresponding sequence position in other 2-oxoglutarate-dependent enzymes. The mutant enzymes were expressed in E. coli and purified to homogeneity. The catalytic activities of [Thr290]FHT and [Ala290]FHT were still significant, albeit greatly reduced to 20 and 8%, respectively, in comparison to the wild-type enzyme, whereas the activity of [Val290]FHT was negligible (about 1%). Kinetic analyses of purified wild-type and mutant enzymes revealed the functional significance of Ser290 for 2-oxoglutarate-binding. The spatial configurations of the related Fe(II)-dependent isopenicillin N and deacetoxycephalosporin C synthases have been reported recently and provide the lead structures for the conformation of other dioxygenases. Circular dichroism spectroscopy was employed to compare the conformation of pure flavanone 3,-hydroxylase with that of isopenicillin N synthase. A double minimum in the far ultraviolet region at 222 nm and 208,210 nm and a maximum at 191,193 nm which are characteristic for ,-helical regions were observed, and the spectra of the two dioxygenases fully matched revealing their close structural relationship. Furthermore, the spectrum remained unchanged after addition of either ferrous ions, 2-oxoglutarate or both of these cofactors, ruling out a significant conformational change of the enzyme on cofactor-binding. [source] Synthesis of Cyclic Peptides by Photochemical Decarboxylation of N -Phthaloyl Peptides in Aqueous SolutionHELVETICA CHIMICA ACTA, Issue 12 2002The synthesis of a variety of cyclic peptides from N -phthaloyl-protected di-, tri-, tetra-, and pentapeptides with different aminocarboxylic acid tethers by photodecarboxylation , initiated by intramolecular electron transfer , has been explored in aqueous media. The progress and the chemoselectivity of the follow-up processes after CO2 extrusion were traced by the respective pH/time-profiles, as well as by the overall change in pH after completion of the reaction. The competition between cyclization and simple oxidative decarboxylation depends on spacer length and geometry, H-bonding interaction between the electron accepting phthalimide CO groups and amide H-atoms, as well as the geometric reorganization coupled with the radical combination step and the formation of the lactam rings. With progressing reaction, hydrolysis of the phthalimide chromophore becomes an increasingly important side reaction due to the constant increase in pH. The use of phosphate-buffered aqueous media consequently improved the cyclization yields. The ground-state interactions between amide groups and the terminal COO, group with the imide CO groups were studied for the model system [N -(phthaloyl)glycyl]sarcosine (1) by NMR spectroscopy where the amide (E/Z)-equilibrium depends on the presence of carboxylate vs. free carboxylic acid, demonstrating the role of H-bonding and metal coordination. [source] Pathways that produce volatile sulphur compounds from methionine in Oenococcus oeniJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2008A. Vallet Abstract Aims:, Determination of pathways involved in synthesis of volatile sulphur compounds (VSC) from methionine by Oenococcus oeni isolated from wine. Methods and Results:, Production of VSC by O. oeni from methionine was investigated during bacterial cultures and in assays performed in the presence of resting cells or protein fractions. Cells of O. oeni grown in a medium supplemented with methionine produced methanethiol, dimethyl disulphide, methionol and 3-(methylthio)propionic acid. Methional was also detected, but only transiently during the exponential growth phase. It was converted to methionol and 3-(methylthio) propionic acid in assays. Although this acid could be produced alternatively from 2-oxo-4-(methylthio) butyric acid (KMBA) by oxidative decarboxylation. In addition, KMBA was a precursor for methanethiol and dimethyl disulphide synthesis. Interestingly, assays with resting cells and protein fractions suggested that a specific enzyme could be involved in this conversion in O. oeni. Conclusion:, This work shows that methional and KMBA are the key intermediates for VSC synthesis from methionine in O. oeni. Putative enzymatic and chemical pathways responsible for the production of these VSC are discussed. Significance and impact of the study:, This work confirms the capacity of O. oeni to metabolize methionine and describes the involvement of potential enzymatic pathways. [source] Temperature responses are a window to the physiology of dark respiration: differences between CO2 release and O2 reduction shed light on energy conservationPLANT CELL & ENVIRONMENT, Issue 7 2008JÖRG KRUSE ABSTRACT We showed that temperature responses of dark respiration for foliage of Pinus radiata could be approximated by Arrhenius kinetics, whereby E0 determines shape of the exponential response and denotes overall activation energy of respiratory metabolism. Reproducible and predictable deviation from strict Arrhenius kinetics depended on foliage age, and differed between RCO2 and RO2. Inhibition of oxygen reduction (RO2) by cyanide (inhibiting COX) or SHAM (inhibiting AOX) resulted in reproducible changes of the temperature sensitivity for RO2, but did not affect RCO2. Enthalpic growth , preservation of electrons in anabolic products , could be approximated with knowledge of four variables: activation energies (E0) for both RCO2 and RO2, and basal rates of respiration at a low reference temperature (RREF). Rates of enthalpic growth by P. radiata needles were large in spring due to differences between RREF of oxidative decarboxylation and that of oxygen reduction, while overall activation energies for the two processes were similar. Later during needle development, enthalpic growth was dependent on differences between E0 for RCO2 as compared with RO2, and increased E0(RO2) indicated greater contributions of cytochrome oxidase to accompany the switch from carbohydrate sink to source. Temperature-dependent increments in stored energy can be calculated as the difference between RCO2,HCO2 and RO2,HO2. [source] | |||||||||||||