The mechanism for the conversion of uric acid into uroxanate and allantoin

Poje, M.; Sokolić-Maravić, Lea

doi:10.1016/s0040-4020(01)90112-7

Cited by 31 publications

(20 citation statements)

References 30 publications

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“…The interconversion between dGh and dIa isomers is best explained by a multistep equilibrium reaction mechanism (Scheme A). Further, this isomerization is expected to follow the same pathway as reported for allantoin, which has been the topic of many studies over the years (Scheme B). − On the basis of the pH dependency observed for the dGh to dIa equilibrium, we propose the first equilibrium involves deprotonation of the guanidinium group (Scheme A). The p K a for this proton transaction is ∼10.1 on the basis of our results (Figure B).…”

Section: Resultsmentioning

confidence: 66%

“…The UV–vis and NMR results were interpreted with the guidance of DFT calculations. Mechanistically, the interconversion between dGh and dIa is proposed to follow a similar pathway as for the isomerization of allantoin, a uric acid oxidation product. − We propose a multistep reaction pathway to describe the pH-dependent equilibrium between dGh and dIa (Scheme A). The key first step involves deprotonation of the guanidinium group of dGh to unmask the nucleophile, allowing attack of this group at the C4 carbon.…”

Section: Discussionmentioning

confidence: 99%

“…Previous studies identified that allantoin can isomerize between two constitutional isomers that differ in the ring atoms (Scheme ). − By analogy to allantoin, dGh can isomerize to iminoallantoin-2′-deoxynucleoside (dIa, Scheme ). In the present study, we determined that a pH-dependent equilibrium exists between dGh and dIa in the nucleoside context with a transition pH = 10.1.…”

Section: Introductionmentioning

confidence: 99%

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pH-Dependent Equilibrium between 5-Guanidinohydantoin and Iminoallantoin Affects Nucleotide Insertion Opposite the DNA Lesion

et al. 2015

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Four-electron oxidation of 2’-deoxyguanosine (dG) yields 5-guanidinohydantoin (dGh) as a product. Previously, we hypothesized that dGh could isomerize to iminoallantoin (dIa) via a mechanism similar to the isomerization of allantoin. The isomerization reaction was monitored by HPLC and found to be pH dependent with a transition pH = 10.1 in which dGh was favored at low pH and dIa was favored at high pH. The structures for these isomers were confirmed by UV-vis, MS, 1H, and 13C NMR. Additionally, the UV-vis and NMR experimental results are supported by density functional theory calculations. A mechanism is proposed to support the pH dependency of the isomerization reaction. Next, we noted the hydantoin ring of dGh mimics thymine, while the iminohydantoin ring of dIa mimics cytosine; consequently, a dGh/dIa site was synthesized in a DNA template strand and standing start primer extension studies were conducted with Klenow fragment exo−. The dATP/dGTP insertion ratio opposite the dGh/dIa site as a function of pH was evaluated from pH 6.5 – 9.0. At pH 6.5 only dATP was inserted, but as the pH increased to 9.0, the amount of dGTP insertion steadily increased. This observation supports dGh to dIa isomerization in DNA with a transition pH of ~8.2.

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Section: Resultsmentioning

confidence: 66%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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pH-Dependent Equilibrium between 5-Guanidinohydantoin and Iminoallantoin Affects Nucleotide Insertion Opposite the DNA Lesion

et al. 2015

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“…Different binding motifs in guanidinium urate and 8-azaxanthinate [2], which presumably reflect the location of negative charge [3], are related by 180° rotation about the N1-C4 axis; the conformational flexibility of Argl76, Gln228, and Phel59 residues in the active cleft allows an induced fit for binding. It is now clear how the stereospecificity of uricase reaction may arise [4][5][6][7][8]. Urate fits snugly into the active pocket, exposing the si-si face with effectively desolvated imidazolone subnucleus to the oxidative attack.…”

Section: Discussionmentioning

confidence: 99%

Crystal structure of guanidinium urate monohydrate, C5H3N4O3(CH6N3) · H2O

Poje

Vicković

2000

Zeitschrift Für Kristallographie - New Crystal Structures

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“…The secondary chemistryo fu rate redox systems, so far as it is known at all, [20] is similarly complicated as in the case of ascorbate [21,22] but has remained unchartered territory to am uch larger extent. Probingm ore deeply into the mechanismsoft he extrinsicc atalystd ecomposition would thusb et ime-consuming, yeto fu ncertain benefitb ecause with any practical application the substrate concentration will be high enough for capturing as ubstantial fraction of e À aq ,w hich automatically diminishes the catalyst poisoning.…”

Section: Preparative Photolysismentioning

confidence: 99%

First Micelle‐Free Photoredox Catalytic Access to Hydrated Electrons for Syntheses and Remediations with a Visible LED or even Sunlight

Naumann

Goez

2018

Chemistry A European J

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Hydrated electrons are super-reductants, yet can be generated with visible light when two photons are pooled, most efficiently through storing the energy of the first photon in a radical pair formed by the reduction of an excited catalyst by a sacrificial donor. All previous such systems for producing synthetically useable amounts of hydrated electrons with an LED in the visible range had to resort to compartmentalization by SDS micelles to curb the performance-limiting recombination of the pair. To overcome micelle-imposed constraints on sustainability and applications, we have instead attached carboxylate groups to a ruthenium (tris)bipyridyl catalyst such that its pentaanionic radical strongly repels the dianionic radical of the bioavailable donor urate. We have explored the influence of the Coulombic interactions on the electron generation by a time-resolved study from microseconds to hours, including for comparison the unsubstituted complex, which forms a monocationic radical, with and without SDS micelles. The new homogeneous electron source is best with regard to stability and total electron output; it has a broader synthetic scope because it does not entail micellar shielding of less hydrophilic compounds, which particularly facilitates cross-couplings; and it tolerates supramolecular containers as carriers of water-insoluble substrates or products. As an application in the field, we demonstrate the solar remediation of a recalcitrant chloro-organic bulk chemical.

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The mechanism for the conversion of uric acid into uroxanate and allantoin

Cited by 31 publications

References 30 publications

pH-Dependent Equilibrium between 5-Guanidinohydantoin and Iminoallantoin Affects Nucleotide Insertion Opposite the DNA Lesion

pH-Dependent Equilibrium between 5-Guanidinohydantoin and Iminoallantoin Affects Nucleotide Insertion Opposite the DNA Lesion

Crystal structure of guanidinium urate monohydrate, C5H3N4O3(CH6N3) · H2O

First Micelle‐Free Photoredox Catalytic Access to Hydrated Electrons for Syntheses and Remediations with a Visible LED or even Sunlight

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