General Base Catalysis of the Aminolysis of Phenyl Acetate by Primary Alkylamines<sup>1</sup>

Jencks, William P.; Gilchrist, Mary.

doi:10.1021/ja00953a020

Cited by 67 publications

(38 citation statements)

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“…Enthalpic effects have also been shown to predominate in systems in which catalysis is much less pronounced, including general base catalysis of the bromination of acetoacetate by glycolate (16), in the covalent catalysis of the hydrolysis of 4-nitrophenyl acetate by imidazole (17), in general base catalysis of the aminolysis of carboxylic esters by alkylamines (18), and in the Mg II -catalyzed methanolysis of ATP (19).…”

Section: Do Primitive Catalysts Act By Lowering δH ‡ ? a Testmentioning

confidence: 99%

Impact of temperature on the time required for the establishment of primordial biochemistry, and for the evolution of enzymes

Stockbridge

Lewis

Yuan

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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All reactions are accelerated by an increase in temperature, but the magnitude of that effect on very slow reactions does not seem to have been fully appreciated. The hydrolysis of polysaccharides, for example, is accelerated 190,000-fold when the temperature is raised from 25 to 100°C, while the rate of hydrolysis of phosphate monoester dianions increases 10,300,000-fold. Moreover, the slowest reactions tend to be the most heat-sensitive. These tendencies collapse, by as many as five orders of magnitude, the time that would have been required for early chemical evolution in a warm environment. We propose, further, that if the catalytic effect of a "proto-enzyme"-like that of modern enzymes-were mainly enthalpic, then the resulting rate enhancement would have increased automatically as the environment became cooler. Several powerful nonenzymatic catalysts of very slow biological reactions, notably pyridoxal phosphate and the ceric ion, are shown to meet that criterion. Taken together, these findings greatly reduce the time that would have been required for early chemical evolution, countering the view that not enough time has passed for life to have evolved to its present level of complexity.activation energy | thermophilic organisms | pyridoxal phosphate | phosphate ester hydrolysis | amino acid decarboxylation W hereas enzyme reactions ordinarily occur in a matter of milliseconds, the same reactions proceed with half-lives of hundreds, thousands, or millions of years in the absence of a catalyst ( Fig. 1) (1). Yet life is believed to have taken hold within the first 25% of Earth's history (2). How could cellular chemistry, and the enzymes that make life possible, have arisen so quickly? Here, we show that because of an extraordinarily sensitive relationship between temperature and the rates of very slow reactions, the time required for early evolution on a warm earth was very much shorter than it might appear. That sensitivity also suggests some likely properties of an evolvable catalyst, and a testable mechanism by which its ability to enhance rates might have been expected to increase as the environment cooled.Rapid substrate turnover is necessary to support the metabolism of an organism at the enzyme concentrations found in cells, but the same reactions, in the absence of enzymes, proceed vastly more slowly (Fig. 1). For example, the decarboxylation of orotidine 5′-phosphate (OMP), the final step in the biosynthesis of pyrimidines-and thus nucleic acids-proceeds with a half-life of 0.017 s at the active site of OMP decarboxylase. In neutral solution in the absence of the enzyme, the same reaction proceeds with a half-life of 78 million years (1). It is natural to ask how enzymes arose to meet so formidable a challenge. The Time Required for Primordial Chemistry to Become EstablishedThe rates of simple reactions, even if they are immeasurably slow at ordinary temperatures, can often be estimated by first determining their rates at elevated temperatures. Plots of the logarithm of the observed rate constants a...

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Section: Do Primitive Catalysts Act By Lowering δH ‡ ? a Testmentioning

confidence: 99%

Impact of temperature on the time required for the establishment of primordial biochemistry, and for the evolution of enzymes

Stockbridge

Lewis

Yuan

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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“…Rate enhancements have been shown to depend primarily on a reduction in ⌬H ‡ , rather than an increase in T⌬S ‡ , in general base catalysis by glycolate of the bromination of acetoacetate (24), in general base catalysis of ester aminolysis by amines (25), in Mg II catalysis of the alcoholysis of ATP (26), in imidazole catalysis of ester hydrolysis (27), and in phase-transfer catalysis of phosphodiester hydrolysis in the presence of cyclohexane (28). Of special interest is the finding that catalytic antibodies for several reactions produce rate enhancements that are entirely enthalpic in origin (29 -31).…”

Section: Figure 2 Entropies Of Activation (T⌬s ‡ ) Plotted As a Funcmentioning

confidence: 99%

Massive Thermal Acceleration of the Emergence of Primordial Chemistry, the Incidence of Spontaneous Mutation, and the Evolution of Enzymes

Wolfenden

2014

Journal of Biological Chemistry

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Kelvin considered it unlikely that sufficient time had elapsed on the earth for life to have reached its present level of complexity. In the warm surroundings in which life first appeared, however, elevated temperatures would have reduced the kinetic barriers to reaction. Recent experiments disclose the profound extent to which very slow reactions are accelerated by elevated temperatures, collapsing the time that would have been required for early events in primordial chemistry before the advent of enzymes. If a primitive enzyme, like model catalysts and most modern enzymes, accelerated a reaction by lowering its enthalpy of activation, then the rate enhancement that it produced would have increased automatically as the environment cooled, quite apart from any improvements in catalytic activity that arose from mutation and natural selection. The chemical events responsible for spontaneous mutation are also highly sensitive to temperature, furnishing an independent mechanism for accelerating evolution.

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“…The nucleophilic atom N (4) of ammonia molecule attaches to the electrophilic atom C (1) from the ester, and a proton H (5) of the ammonia transfers to the oxygen atom O (3) on the acyloxy bond. The transition state CTS has a four-membered-ring structure composed of C (1) , O (3) , H (5) and N (4) atoms. The IRC calculations in the reverse and forward directions from the transition state cause producing of the reaction complex and product complex, which are designated C1C and C2C, respectively.…”

Section: Substituent Effects In the Gas Phasementioning

confidence: 99%

“…For both addition and elimination steps, proton transfers are involved to maintain neutrality when the tetrahedral intermediates are formed. The stepwise mechanism starts with the addition of N (4) -H (5) bond from ammonia molecule to the C (1) @O (2) double bond in the ester molecular, and the first transition state TS1 has a four-membered ring constituted by C (1) , O (2) , H (5) and N (4) atoms. The imaginary vibrational frequencies of the second, third and fourth steps are linked to the bond rotations, mainly the changes of dihedral angles.…”

Section: Substituent Effects In the Gas Phasementioning

confidence: 99%

“…The reaction of the aminolysis of esters is under active investigation as the model for the formation of peptide bonds by using experimental and theoretical methods [1][2][3][4][5][6][7][8][9][10][11][12]. Generally, three possible pathways which conform to the available kinetic results were discussed in literature: (a) the concerted pathway where the proton transfer occurs simultaneously to the formation of C-N bond and cleavage of C-O single bond; (b) the stepwise mechanism through neutral tetrahedral intermediates (addition/elimination pathway); and (c) the stepwise process through zwitterionic intermediates.…”

Section: Introductionmentioning

confidence: 99%

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The substituent effects of the leaving groups on the aminolysis of phenyl acetates: DFT studies

Zeng

Xia

et al. 2008

Chemical Physics

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General Base Catalysis of the Aminolysis of Phenyl Acetate by Primary Alkylamines¹

Cited by 67 publications

References 0 publications

Impact of temperature on the time required for the establishment of primordial biochemistry, and for the evolution of enzymes

Impact of temperature on the time required for the establishment of primordial biochemistry, and for the evolution of enzymes

Massive Thermal Acceleration of the Emergence of Primordial Chemistry, the Incidence of Spontaneous Mutation, and the Evolution of Enzymes

The substituent effects of the leaving groups on the aminolysis of phenyl acetates: DFT studies

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General Base Catalysis of the Aminolysis of Phenyl Acetate by Primary Alkylamines1

Cited by 67 publications

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Impact of temperature on the time required for the establishment of primordial biochemistry, and for the evolution of enzymes

Impact of temperature on the time required for the establishment of primordial biochemistry, and for the evolution of enzymes

Massive Thermal Acceleration of the Emergence of Primordial Chemistry, the Incidence of Spontaneous Mutation, and the Evolution of Enzymes

The substituent effects of the leaving groups on the aminolysis of phenyl acetates: DFT studies

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General Base Catalysis of the Aminolysis of Phenyl Acetate by Primary Alkylamines¹