179. Experiments with heavy water on the acid hydrolysis of esters and the alkaline decomposition of diacetone alcohol

Nelson, W. E.; Butler, J. A. V.

doi:10.1039/jr9380000957

Cited by 24 publications

(9 citation statements)

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“…Adenylation in the wild-type enzyme was found to be linearly dependent on the mole fraction of D 2 O (n) (Figure 6A and B). The plots were fit into a simplified Gross-Butler equation, 47 with the isotopic fractiona-tion factor for the transition state proton being 0.42 for 1 (SKIE app = 2.1) at pL 6.6 and 0.88 for 1 (SKIE app = 1.1) at pL 8.0 (Table 3). Thus, although we cannot completely exclude the possibility of more than one proton in flight, the results of these studies are consistent with the transfer of a single proton during the adenylation step.…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

Caught before Released: Structural Mapping of the Reaction Trajectory for the Sofosbuvir Activating Enzyme, Human Histidine Triad Nucleotide Binding Protein 1 (hHint1)

et al. 2017

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Human histidine triad nucleotide binding protein 1 (hHint1) is classified as an efficient nucleoside phosphoramidase and acyl-adenosine monophosphate hydrolase. Human Hint1 has been shown to be essential for the metabolic activation of nucleotide antiviral pronucleotides (i.e., proTides), such as the FDA approved hepatitis C drug, sofosbuvir. The active site of hHint1 comprises an ensemble of strictly conserved histidines, including nucleophilic His112. To structurally investigate the mechanism of hHint1 catalysis, we have designed and prepared nucleoside thiophosphoramidate substrates that are able to capture the transiently formed nucleotidylated-His112 intermediate (E*) using time-dependent crystallography. Utilizing a catalytically inactive hHint1 His112Asn enzyme variant and wild-type enzyme, the enzyme-substrate (ES) and product (EP) complexes were also cocrystallized, respectively, thus providing a structural map of the reaction trajectory. On the basis of these observations and the mechanistic necessity of proton transfers, proton inventory studies were carried out. Although we cannot completely exclude the possibility of more than one proton in flight, the results of these studies were consistent with the transfer of a single proton during the formation of the intermediate. Interestingly, structural analysis revealed that the critical proton transfers required for intermediate formation and hydrolysis may be mediated by a conserved active site water channel. Taken together, our results provide mechanistic insights underpinning histidine nucleophilic catalysis in general and hHint1 catalysis, in particular, thus aiding the design of future proTides and the elucidation of the natural function of the Hint family of enzymes.

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Section: ■ Materials and Methodsmentioning

confidence: 99%

Caught before Released: Structural Mapping of the Reaction Trajectory for the Sofosbuvir Activating Enzyme, Human Histidine Triad Nucleotide Binding Protein 1 (hHint1)

et al. 2017

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“…Thus the zero-point energies of H-0 and D-0 bonds are closer in the ion than in water, making equilibrium toward the ion less favorable in DzO than in €LO. (165); curve e, base-catalyzed decomposition of diacetone alcohol (165) ; curve f , acid-catalyzed mutarotation of glucose (86) ; curve g, acetate ion-catalyzed mutarotation of glucose (86); curve h, base-catalyzed decomposition of nitramide (125). Other reactions which have been studied are: the acid-catalyzed hydrolysis of ethyl formate (165), the acidcatalyzed hydrolysis of ethyl orthoformate (30), the bromination of acetone (184), and the alcoholic fermentation of glucose and sucrose (180).…”

Section: A Acid Catalysismentioning

confidence: 99%

The Deuterium Isotope Effect

Wiberg¹

1955

Chem. Rev.

721

303

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“…PI results in the literature for the acid-catalysed hydrolyses of ethyl formate [6], methyl acetate [7] and ethyl acetate [8] are described by equation (5):…”

Section: Resultsmentioning

confidence: 99%

“…The intended test is to produce the PI of the k 1 process from the known behaviour of the H + catalysed reaction [6][7][8], with further comparison to results on the water-catalysed hydrolyses of esters and carboxylic anhydrides.…”

Section: Introductionmentioning

confidence: 99%

The proton inventory technique in a dual mechanistic system: the spontaneous hydrolysis of ethyl formate^†

Mata‐Segreda

2007

Isotopes in Environmental and Health Studies

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Ethyl formate undergoes spontaneous hydrolysis through two parallel mechanistic pathways: water catalysis and specific hydrogen-ion catalysis. The proton inventory of the water reaction at 37.0 ( degrees )C was determined from the overall conversion curves, in H(2)O/D(2)O mixtures of deuterium atom fraction n, resulting in k(1)(n)=(2.1+/-0.1)x10(-5) s(-1) (1-n+0.42 n) (1-n+0.83 n)(2), in agreement with the results of six other cases of carboxylic acid derivatives. This result contributes to the validation of the accuracy of the proton inventory technique.

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179. Experiments with heavy water on the acid hydrolysis of esters and the alkaline decomposition of diacetone alcohol

Cited by 24 publications

References 0 publications

Caught before Released: Structural Mapping of the Reaction Trajectory for the Sofosbuvir Activating Enzyme, Human Histidine Triad Nucleotide Binding Protein 1 (hHint1)

Caught before Released: Structural Mapping of the Reaction Trajectory for the Sofosbuvir Activating Enzyme, Human Histidine Triad Nucleotide Binding Protein 1 (hHint1)

The Deuterium Isotope Effect

The proton inventory technique in a dual mechanistic system: the spontaneous hydrolysis of ethyl formate^†

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179. Experiments with heavy water on the acid hydrolysis of esters and the alkaline decomposition of diacetone alcohol

Cited by 24 publications

References 0 publications

Caught before Released: Structural Mapping of the Reaction Trajectory for the Sofosbuvir Activating Enzyme, Human Histidine Triad Nucleotide Binding Protein 1 (hHint1)

Caught before Released: Structural Mapping of the Reaction Trajectory for the Sofosbuvir Activating Enzyme, Human Histidine Triad Nucleotide Binding Protein 1 (hHint1)

The Deuterium Isotope Effect

The proton inventory technique in a dual mechanistic system: the spontaneous hydrolysis of ethyl formate†

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The proton inventory technique in a dual mechanistic system: the spontaneous hydrolysis of ethyl formate^†