Hydrolysis of thioimidate esters. II. Evidence for the formation of three species of the tetrahedral intermediate

Chaturvedi, Rama K.; Schmir, Gaston L.

doi:10.1021/ja01031a040

Cited by 29 publications

(14 citation statements)

References 4 publications

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“…It has been shown for the chemical hydrolysis of thioimidate esters [34,35] that the formation of thiol ester is favored in acidic medium (pH < 2.7), whereas at higher pH values (pH > 2.7) the formation of amide dominates. This result was explained by a facilitated elimination of NH 3 caused by protonation of the amino group in the tetrahedral intermediate.…”

Section: Discussionmentioning

confidence: 99%

Characterization and synthetic applications of recombinant AtNIT1 from Arabidopsis thaliana

Oßwald¹,

Wajant²,

Effenberger³

2002

European Journal of Biochemistry

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The nitrilase AtNIT1 from Arabidopsis thaliana was overexpressed in Escherichia coli with an N-terminal His 6 tag and puri®ed by zinc chelate anity chromatography in a single step almost to homogeneity in a 68% yield with a speci®c activity of 34.1 Uámg . The native enzyme ( 450 kDa) consists of 11±13 subunits (38 kDa). The temperature optimum was determined to be 35°C, and a pH optimum of 9 was found. Thus, recombinant AtNIT1 resembles in its properties the native enzyme and the nitrilase from Brassica napus. The stability of AtNIT1 could be signi®cantly improved by the addition of dithiothreitol and EDTA. The substrate range of AtNIT1 diers considerably from those of bacterial nitrilases.Aliphatic nitriles are the most eective substrates, showing increasing rates of hydrolysis with increasing size of the residues, as demonstrated in the series butyronitrile, octanenitrile, phenylpropionitrile. In comparison with 3-indolylacetonitrile, the rate of hydrolysis of 3-phenylpropionitrile is increased by a factor of 330, and the K m value is reduced by a factor of 23. With the exception of uoro, substituents in the a position to the nitrile function completely inhibit the hydrolysis.

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Section: Discussionmentioning

confidence: 99%

Characterization and synthetic applications of recombinant AtNIT1 from Arabidopsis thaliana

Oßwald¹,

Wajant²,

Effenberger³

2002

European Journal of Biochemistry

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“…However, the used conditions are probably not basic enough to allow such deprotonation, so that a classical Pinner [23] type mechanism seems more plausible. As it is usual [24] that the hydrolysis of thioimidates yields mixtures of thioesters and amides, it is noticeable that in this case, the amide 5 , which would result from an alternative final ring opening, was not observed.…”

Section: Resultsmentioning

confidence: 65%

Chemistry of Homocysteine Thiolactone in A Prebiotic Perspective

Shalayel

Vallée

2019

Life

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Homocysteine is a non-proteinogenic sulfur-containing amino acid. Like cysteine, it can form disulfide bridges and complex metallic cations. It is also closely related to methionine, the first amino acid in the synthesis of all contemporary proteins. Furthermore, its cyclized form, a five-membered ring thiolactone, is stable in acidic and neutral water. Here, we demonstrate that this thiolactone may have been formed in the primitive ocean directly from the Strecker precursor of homocysteine, an aminonitrile. Even though it is poorly reactive, this thiolactone may be open by some amines, yielding amides which, in turn, could be the precursors of longer peptides.

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“…The dipeptide (Cys‐Gly) had a similar rate of cyclization to Cys, while the methyl ester derivative of cysteine (CysOMe) cyclized approximately 150 times more slowly. With a p K a value of around 7, the thioimidate imine was unlikely to be mostly protonated at pH 8.0, which was a prerequisite for nucleophilic attack at a thioimidate carbon during thioimidate hydrolysis . Previous computational studies suggested intramolecular proton transfer from the protonated terminal amine to the neutral imine for the reaction between CBT and Cys .…”

Section: Resultsmentioning

confidence: 99%

“…Therefore,t he effective concentration of the nucleophile must dominate to account for the rate difference,w hich is consistent with the intramolecular cyclization rates of bifunctional compounds,w here 6-membered rings are formed approximately 30-100 times more slowly than 5-membered rings. [28][29][30][31] Thed ipeptide (Cys-Gly) had as imilar rate of cyclization to Cys,w hile the methyl ester derivative of cysteine (CysOMe) cyclized approximately 150 times more slowly.W ith ap K a value of around 7, [32,33] the thioimidate imine was unlikely to be mostly protonated at pH 8.0, which was ap rerequisite for nucleophilic attack at at hioimidate carbon during thioimidate hydrolysis. [33] Previous computational studies suggested intramolecular proton transfer from the protonated terminal amine to the neutral imine for the reaction between CBT and Cys.…”

Section: Angewandte Chemiementioning

confidence: 99%

Single‐Molecule Observation of Intermediates in Bioorthogonal 2‐Cyanobenzothiazole Chemistry

et al. 2020

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We report a single‐molecule mechanistic investigation into 2‐cyanobenzothiazole (CBT) chemistry within a protein nanoreactor. When simple thiols reacted reversibly with CBT, the thioimidate monoadduct was approximately 80‐fold longer‐lived than the tetrahedral bisadduct, with important implications for the design of molecular walkers. Irreversible condensation between CBT derivatives and N‐terminal cysteine residues has been established as a biocompatible reaction for site‐selective biomolecular labeling and imaging. During the reaction between CBT and aminothiols, we resolved two transient intermediates, the thioimidate and the cyclic precursor of the thiazoline product, and determined the rate constants associated with the stepwise condensation, thereby providing critical information for a variety of applications, including the covalent inhibition of protein targets and dynamic combinatorial chemistry.

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Hydrolysis of thioimidate esters. II. Evidence for the formation of three species of the tetrahedral intermediate

Cited by 29 publications

References 4 publications

Characterization and synthetic applications of recombinant AtNIT1 from Arabidopsis thaliana

Characterization and synthetic applications of recombinant AtNIT1 from Arabidopsis thaliana

Chemistry of Homocysteine Thiolactone in A Prebiotic Perspective

Single‐Molecule Observation of Intermediates in Bioorthogonal 2‐Cyanobenzothiazole Chemistry

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