- In Vitro Reconstitution of a Five-Step Pathway for Bacterial Ergothioneine Catabolism
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Ergothioneine is a histidine-derived sulfur metabolite that is biosynthesized by bacteria and fungi. Plants and animals absorb ergothioneine as a micronutrient from their environment or nutrition. Several different mechanisms of microbial ergothioneine production have been described in the past ten years. Much less is known about the genetic and structural basis for ergothioneine catabolism. In this report, we describe the in vitro reconstitution of a five-step pathway that degrades ergothioneine to l-glutamate, trimethylamine, hydrogen sulfide, carbon dioxide, and ammonia. The first two steps are catalyzed by the two enzymes ergothionase and thiourocanate hydratase. These enzymes are closely related to the first two enzymes in histidine catabolism. However, the crystal structure of thiourocanate hydratase from the firmicute Paenibacillus sp. reveals specific structural features that strictly differentiate the activity of this enzyme from that of urocanate hydratases. The final two steps are catalyzed by metal-dependent hydrolases that share most homology with the last two enzymes in uracil catabolism. The early and late part of this pathway are connected by an entirely new enzyme type that catalyzes desulfurization of a thiohydantoin intermediate. Homologous enzymes are encoded in many soil-dwelling firmicutes and proteobacteria, suggesting that bacterial activity may have a significant impact on the environmental availability of ergothioneine.
- Beliaeva, Mariia A.,Leisinger, Florian,Seebeck, Florian P.
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p. 397 - 403
(2021/03/08)
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- Water proton NMR detection of amide hydrolysis and diglycine dimerization
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The transverse relaxation rate of water protons R2(1H2O) is found to be sensitive to amide hydrolysis and diglycine dimerization. The results demonstrate the feasibility of using R2(1H2O) as a diagnostic tool to detect chemical changes in aqueous solutions. Potential applications include drug product formulation and inspection.
- Briggs, Katharine T.,Taraban, Marc B.,Bruce Yu
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p. 7003 - 7006
(2018/07/05)
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- Direct evidence that an extended hydrogen-bonding network influences activation of pyridoxal 5'-phosphate in aspartate aminotransferase
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Pyridoxal 5'-phosphate (PLP) is a fundamental, multifunctional enzyme cofactor used to catalyze a wide variety of chemical reactions involved in amino acid metabolism. PLP-dependent enzymes optimize specific chemical reactions by modulating the electronic states of PLP through distinct active site environments. In aspartate aminotransferase (AAT), an extended hydrogen bond network is coupled to the pyridinyl nitrogen of the PLP, influencing the electrophilicity of the cofactor. This network, which involves residues Asp-222, His-143, Thr-139, His-189, and structural waters, is located at the edge of PLP opposite the reactive Schiff base. We demonstrate that this hydrogen bond network directly influences the protonation state of the pyridine nitrogen of PLP, which affects the rates of catalysis. We analyzed perturbations caused by single-and double-mutant variants using steady-state kinetics, high resolution X-ray crystallography, and quantum chemical calculations. Protonation of the pyridinyl nitrogen to form a pyridinium cation induces electronic delocalization in the PLP, which correlates with the enhancement in catalytic rate in AAT. Thus, PLP activation is controlled by the proximity of the pyridinyl nitrogen to the hydrogen bond microenvironment. Quantum chemical calculations indicate that Asp-222, which is directly coupled to the pyridinyl nitrogen, increases the pKa of the pyridine nitrogen and stabilizes the pyridinium cation. His-143 and His-189 also increase the pKa of the pyridine nitrogen but, more significantly, influence the position of the proton that resides between Asp-222 and the pyridinyl nitrogen. These findings indicate that the second shell residues directly enhance the rate of catalysis in AAT.
- Dajnowicz, Steven,Parks, Jerry M.,Hu, Xiche,Gesler, Korie,Kovalevsky, Andrey Y.,Mueser, Timothy C.
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p. 5970 - 5980
(2017/04/17)
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- A thermodynamic insight into the recognition of hydrophilic and hydrophobic amino acids in pure water by aza-scorpiand type receptors
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Interactions of different hydrophilic (His, Asp, Glu,) and hydrophobic (Ala, Phe, Tyr, Trp) amino acids in water with a scorpiand aza-macrocycle (L1) containing a pyridine group in the ring and its derivative (L2) bearing a naphthalene group in the tail have been analysed by potentiometric and calorimetric measurements. Theoretical calculations corroborate that major attractive forces that hold the adduct together are hydrogen bonds and salt-bridges, even though other interactions such as π-stacking or NH+...π may contribute in the case of hydrophobic amino acids and L2. Calorimetric measurements indicate that the interactions between L1 and the different amino acids are principally driven by entropy, often associated with solvation/desolvation processes.
- Blasco, Salvador,Verdejo, Begoa,Bazzicalupi, Carla,Bianchi, Antonio,Giorgi, Claudia,Soriano, Concepcin,Garca-Espaa, Enrique
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supporting information
p. 843 - 850
(2015/02/19)
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- Mussel-inspired plasmonic nanohybrids for light harvesting
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Core-shell plasmonic nanohybrids are synthesized through a simple solutionbased process utilizing mussel-inspired polydopamine (PDA). The multi-purpose PDA not only facilitates plasmonic metal formation, but also serves as a scaffold to incorporate photosensitizers around the metal cores, as well as an adhesive between the nanohybrids and the substrate. The resulting plasmonic assembly exhibits highly enhanced light absorption in photo catalytic systems to augment artificial photosynthesis.
- Lee, Minah,Kim, Jong Uk,Lee, Joon Seok,Lee, Byung Il,Shin, Jonghwa,Park, Chan Beum
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p. 4463 - 4468
(2014/07/22)
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- An antenna-sensitized nitroindoline precursor to enable photorelease of L-glutamate in high concentrations
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1-Acyl-7-nitroindolines are useful reagents for rapid release of carboxylates upon flash photolysis in aqueous solution and have been particularly effective for rapid (submicrosecond) release of neuroactive amino acids such as L-glutamate in biological ex
- Papageorgiou, George,Ogden, David,Corrie, John E. T.
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p. 7228 - 7233
(2007/10/03)
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- Thermodynamics of reactions catalysed by branched-chain-amino-acid transaminase
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Apparent equilibrium constants and calorimetric enthalpies of reaction have been measured for reactions catalysed by branched-chain-amino-acid transaminase. The following biochemical reactions have been studied at the temperature 298.15 K and in the pH ra
- Tewari, Yadu B.,Goldberg, Robert N.,Rozzell, J. David
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p. 1381 - 1398
(2007/10/03)
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- Desyl esters of amino acid neurotransmitters. Phototriggers for biologically active neurotransmitters
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The application of the desyl or 2-oxo-1,2-diphenylethyl moiety as a photolabile ligand for the release of phosphates such as cAMP and inorganic phosphate (P(i))1,2 is extended to include selected excitatory amino acids. The synthesis and photochemical studies of N- and O-desyl-caged versions of the endogenous amino acid neurotransmitters glutamate and γ-aminobutyric acid (GABA) are reported. Photolysis at 350 nm of solutions of γ-O-desyl glutamate (11) and O-desyl GABA (14) in 1:1 H2O-acetonitrile cleanly produced free glutamate and GABA, respectively, with rate constants of ca. 107 s-1; 2-phenylbenzo[b]furan (2) was the only photobyproduct detected by HPLC. Photolysis quantum efficiencies for the disappearance of O-desyl amino acid esters were in the range of 0.29-0.31, and the appearance efficiencies of furan 2 (and the corresponding amino acid) were 0.14. The photolysis of 14 was efficiently quenched with sodium 2-naphthalenesulfonate, yielding a triplet lifetime of ca. 10 ns. Photolysis of 11 in mammalian brain tissue slices resulted in glutamate receptor activation, as indicated by whole cell electrophysiological measurements. Photolysis of the other desyl amino acids resulted in decomposition and produced several products but did not lead to the formation of furan 2.
- Gee, Kyle R.,Kueper III, L. William,Barnes, Jeffrey,Dudley, Gregory,Givens, Richard S.
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p. 1228 - 1233
(2007/10/03)
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