- An Unusual Elimination-Addition (Keten-mediated) Aminolysis Pathway for Malonic S-Thioesters, including S-Malonyl Coenzyme A
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S-Monoesters of malonic acid, including S-malonyl coenzyme A itself, undergo aminolysis via a novel proton-assisted (keten-mediated) E1cB pathway.
- Douglas, Kenneth T.,Alborz, Manoochehr,Rullo, Gregory R.,Yaggi, Norbert F.
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- Mechanism of inhibition of aliphatic epoxide carboxylation by the coenzyme M analog 2-bromoethanesulfonate
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The bacterial metabolism of epoxypropane formed from propylene oxidation uses the atypical cofactor coenzyme M (CoM, 2-mercaptoethanesulfonate) as the nucleophile for epoxide ring opening and as a carrier of intermediates that undergo dehydrogenation, reductive cleavage, and carboxylation to form acetoacetate in a three-step metabolic pathway. 2-Ketopropyl-CoM carboxylase/oxidoreductase (2-KPCC), the terminal enzyme of this pathway, is the only known member of the disulfide oxidoreductase family of enzymes that is a carboxylase. In the present work, the CoM analog 2-bromoethanesulfonate (BES) is shown to be a reversible inhibitor of 2-KPCC and hydroxypropyl-CoM dehydrogenase but not of epoxyalkane:CoM transferase. Further investigations revealed that BES is a time-dependent inactivator of dithiothreitol-reduced 2-KPCC, where the redox active cysteines are in the free thiol forms. BES did not inactivate air-oxidized 2-KPCC, where the redox active cysteine pair is in the disulfide form. The inactivation of 2-KPCC exhibited saturation kinetics, and CoM slowed the rate of inactivation. Mass spectral analysis demonstrated that BES inactivation of reduced 2-KPCC occurs with covalent modification of the interchange thiol (Cys82) by a group with a molecular mass identical to that of ethylsulfonate. The flavin thiol Cys87 was not alkylated by BES under reducing conditions, and no amino acid residues were modified by BES in the oxidized enzyme. The UV-visible spectrum of BES-modifed 2-KPCC showed the characteristic charge transfer absorbance expected with alkylation at Cys82. These results identify BES as a reactive CoM analog that specifically alkylates the interchange thiol that facilitates thioether bond cleavage and enolacetone formation during catalysis.
- Boyd, Jeffrey M.,Clark, Daniel D.,Kofoed, Melissa A.,Ensign, Scott A.
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- 3-Keto-5-aminohexanoate cleavage enzyme: A common fold for an uncommon claisen-type condensation
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The exponential increase in genome sequencing output has led to the accumulation of thousands of predicted genes lacking a proper functional annotation. Among this mass of hypothetical proteins, enzymes catalyzing new reactions or using novel ways to cata
- Bellinzoni, Marco,Bastard, Karine,Perret, Alain,Zaparucha, Anne,Perchat, Nadia,Vergne, Carine,Wagner, Tristan,De Melo-Minardi, Raquel C.,Artiguenave, Francois,Cohen, Georges N.,Weissenbach, Jean,Salanoubat, Marcel,Alzari, Pedro M.
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- Kinetic and Structural Analysis of Two Linkers in the Tautomerase Superfamily: Analysis and Implications
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The tautomerase superfamily (TSF) is a collection of enzymes and proteins that share a simple β-α-β structural scaffold. Most members are constructed from a single-core β-α-β motif or two consecutively fused β-α-β motifs in which the N-terminal proline (Pro-1) plays a key and unusual role as a catalytic residue. The cumulative evidence suggests that a gene fusion event took place in the evolution of the TSF followed by duplication (of the newly fused gene) to result in the diversification of activity that is seen today. Analysis of the sequence similarity network (SSN) for the TSF identified several linking proteins ("linkers") whose similarity links subgroups of these contemporary proteins that might hold clues about structure-function relationship changes accompanying the emergence of new activities. A previously uncharacterized pair of linkers (designated N1 and N2) was identified in the SSN that connected the 4-oxalocrotonate tautomerase (4-OT) and cis-3-chloroacrylic acid dehalogenase (cis-CaaD) subgroups. N1, in the cis-CaaD subgroup, has the full complement of active site residues for cis-CaaD activity, whereas N2, in the 4-OT subgroup, lacks a key arginine (Arg-39) for canonical 4-OT activity. Kinetic characterization and nuclear magnetic resonance analysis show that N1 has activities observed for other characterized members of the cis-CaaD subgroup with varying degrees of efficiencies. N2 is a modest 4-OT but shows enhanced hydratase activity using allene and acetylene compounds, which might be due to the presence of Arg-8 along with Arg-11. Crystallographic analysis provides a structural context for these observations.
- Baas, Bert-Jan,Babbitt, Patricia C.,De Ruijter, Marieke,Erwin, Kaci,Johnson, William H.,Kaoud, Tamer S.,Lancaster, Emily B.,Levieux, Jake A.,Medellin, Brenda P.,Moreno, R. Yvette,Whitman, Christian P.,Zhang, Yan Jessie
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- carba Nicotinamide Adenine Dinucleotide Phosphate: Robust Cofactor for Redox Biocatalysis
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Here we report a new robust nicotinamide dinucleotide phosphate cofactor analog (carba-NADP+) and its acceptance by many enzymes in the class of oxidoreductases. Replacing one ribose oxygen with a methylene group of the natural NADP+ was found to enhance stability dramatically. Decomposition experiments at moderate and high temperatures with the cofactors showed a drastic increase in half-life time at elevated temperatures since it significantly disfavors hydrolysis of the pyridinium-N?glycoside bond. Overall, more than 27 different oxidoreductases were successfully tested, and a thorough analytical characterization and comparison is given. The cofactor carba-NADP+ opens up the field of redox-biocatalysis under harsh conditions.
- D?ring, Manuel,Sieber, Volker,Simon, Robert C.,Tafertshofer, Georg,Zachos, Ioannis
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supporting information
p. 14701 - 14706
(2021/05/13)
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- Process for preparing hyperpolarized substrates and method for MRI
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The present invention generally relates to a process for the preparation of aqueous solutions of hyperpolarized molecules ready for use in in-vivo MR diagnostic imaging, the use thereof as MRI contrast agent in investigation methods for producing diagnostic MR images of a human or non-human animal body organ, region or tissue.
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Page/Page column 29
(2017/08/01)
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- Electrochemical Carboxylation Coupled with Nitrite Reduction Catalyzed by (2-) and (3-)
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The controlled-potential electrolysis of CO2-saturated CH3CN containing Fe4S4(SPh)4(-2), NO2-, PhCOCH3, and a dehydration agent at -1.25 V vs SCE catalytically produced not only N2 accompanied by a small amount of N2O but also PhCOCH2COO(1-) with the mol
- Tanaka, Koji,Wakita, Ryuhei,Tanaka, Toshio
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p. 2428 - 2433
(2007/10/02)
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