Some Aspects of Mechanism and Catalysis for Carbonyl Addition Reactions<sup>1</sup>

Amaral, Luciano; Sandstrom, W.A.; Cordes, E. H.

doi:10.1021/ja00962a027

Cited by 51 publications

(21 citation statements)

References 6 publications

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“…This also explains the very low reactivity of the D298A mutant toward phenylhydrazine (k obs WT /k obs D298A ) ∼170, Table 2); the reaction with phenylhydrazine also involves a dehydration step prior to the hydrazone formation (48). The hydrazino amino group of phenylhydrazine has a pK a of 5.25 (49), and therefore, its deprotonation at neutral pH needs little assistance by Asp298, supporting the greater contribution of Asp298 to the dehydration from the carbinolamine (steps C f D f E) than to the initial deprotonation of the substrate amino group (step A f B). Hence, the first intermediate observed by the presteady-state kinetic analysis is TPQ ssb , with the substrate amino nitrogen atom attached to the C5 carbon of TPQ in an imine double bond, and the carboxylate of Asp298 is deprotonated again (E).…”

Section: Discussionmentioning

confidence: 96%

Kinetic and Structural Studies on the Catalytic Role of the Aspartic Acid Residue Conserved in Copper Amine Oxidase^,

et al. 2006

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Copper amine oxidase contains a post-translationally generated quinone cofactor, topa quinone (TPQ), which mediates electron transfer from the amine substrate to molecular oxygen. The overall catalytic reaction is divided into the former reductive and the latter oxidative half-reactions based on the redox state of TPQ. In the reductive half-reaction, substrate amine reacts with the C5 carbonyl group of the oxidized TPQ, forming the substrate Schiff base (TPQ(ssb)), which is then converted to the product Schiff base (TPQ(psb)). During this step, an invariant Asp residue with an elevated pKa is presumed to serve as a general base accepting the alpha proton of the substrate. When Asp298, the putative active-site base in the recombinant enzyme from Arthrobacter globiformis, was mutated into Ala, the catalytic efficiency dropped to a level of about 10(6) orders of magnitude smaller than the wild-type (WT) enzyme, consistent with the essentiality of Asp298. Global analysis of the slow UV/vis spectral changes observed during the reductive half-reaction of the D298A mutant with 2-phenylethylamine provided apparent rate constants for the formation and decay of TPQ(ssb) (k(obs) = 4.7 and 4.8 x 10(-4) s(-1), respectively), both of which are markedly smaller than those of the WT enzyme determined by rapid-scan stopped-flow analysis (k(obs) = 699 and 411 s(-1), respectively). Thus, Asp298 plays important roles not only in the alpha-proton abstraction from TPQ(ssb) but also in other steps in the reductive half-reaction. X-ray diffraction analyses of D298A crystals soaked with the substrate for 1 h and 1 week revealed the structures of TPQ(ssb) and TPQ(psb), respectively, as pre-assigned by single-crystal microspectrophotometry. Consistent with the stereospecificity of alpha-proton abstraction, the pro-S alpha-proton of TPQ(ssb) to be abstracted is positioned nearly perpendicularly to the plane formed by the Schiff-base imine double bond conjugating with the quinone ring of TPQ, so that the orbitals of sigma and pi electrons maximally overlap in the conjugate system. More intriguingly, the pro-S alpha proton of the substrate is released stereospecifically even in the reaction catalyzed by the base-lacking D298A mutant. On the basis of these results, we propose that the stereospecificity of alpha-proton abstraction is primarily determined by the conformation of TPQ(ssb), rather than the relative geometry of TPQ and the catalytic base.

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Section: Discussionmentioning

confidence: 96%

Kinetic and Structural Studies on the Catalytic Role of the Aspartic Acid Residue Conserved in Copper Amine Oxidase^,

et al. 2006

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“…The pH‐rate behavior of carbonyl amine reactions represent classic examples of pH‐rate profile inflections associated with changes in the rate‐determining step of a complex reaction pathway in contrast to the more common cases of pH‐rate profile inflections due to substrate ionization 1–5. The mechanism for carbonyl‐amine reactions requires the presence of the deprotonated amine which acts a nucelophile in its initial attack on a susceptible carbonyl (e.g., an aldehyde) leading to the formation of a tetrahedral intermediate.…”

Section: Introductionmentioning

confidence: 99%

“…Subsequent dehydration of the intermediate gives rise to an imine. Bell‐shaped pH rate profiles have been observed for the reactions of aliphatic 5 and moderately basic aromatic amines (e.g., hydroxylamine p K a = 6, aniline p K a = 4.6) with simple aldehydes (e.g., benzaldehydes) 1–3, 5, 6. For ionizable substrates, bell‐shaped profiles occur when the substrate is present in the reaction milieu in at least three distinguishable ionic forms (e.g., the substrate possesses at least two overlapping p K a values).…”

Section: Introductionmentioning

confidence: 99%

Glycosylation of aromatic amines II: Kinetics and mechanisms of the hydrolytic reaction between kynurenine and glucose

Gokhale

Kirsch

2009

Journal of Pharmaceutical Sciences

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“…Meanwhile, our attention has been focusing on the feasibility of transoximization reaction (oxime-exchange reaction) between small O-substituted hydroxylamine derivatives and oligosaccharides trapped onto polymers through an oxime-bond formation. Transoximization has been implemented recently in a number of cases concerning the development of dynamic combinatorial libraries since the late Nineties, [13][14][15][16][17][18][19] but was never applied to the hemiacetal group present at the reducing terminal of oligosaccharide. We thought that transoximization may be perfectly compatible with glycoblotting technology since transoximization may allow simultaneous derivatization upon releasing from the blotting polymer by adding aminooxy functionalized low molecular weight compound(s).…”

Section: Introductionmentioning

confidence: 99%

One‐Pot Solid‐Phase Glycoblotting and Probing by Transoximization for High‐Throughput Glycomics and Glycoproteomics

Shimaoka

Kuramoto

Furukawa

et al. 2007

Chemistry A European J

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The development of rapid and efficient methods for high-throughput protein glycomics is of growing importance because the glycoform-focused reverse proteomics/genomics strategy will greatly contribute to the discovery of novel biomarkers closely related to cellular development, differentiation, growth, and aging as well as a variety of diseases such as cancers and viral infection. Recently, we communicated that rapid and efficient purification of carbohydrates can be achieved by employing sugar-specific chemical ligation with aminooxy-functionalized polymers, which we termed "glycoblotting" (see S.-I. Nishimura et al., Angew. Chem. 2005, 117, 93-98; Angew. Chem. Int. Ed. 2005, 44, 91-96). The chemoselective blotting of oligosaccharides present in crude biological materials onto synthetic polymers relies on the unique oxime-bond formation between aminooxy group displayed on the supporting materials and aldehyde/ketone group at the reducing terminal of all oligosaccharides, thus enabling highly selective and rapid oligosaccharide purification. Aiming to improve the detection sensitivity of the released oligosaccharides, we introduce here a novel strategy for one-pot solid-phase glycoblotting and probing by transoximization. We found that oligosaccharides captured by the polymer supports via the oxime bond can be released in the presence of excess O-substituted aminooxy derivatives in a weakly acidic condition. The released oligosaccharides could be recovered as newly formed oxime derivatives of the O-substituted aminooxy compound added, thus demonstrating the simultaneous releasing and probing. In addition, we synthesized a novel aminooxy-functionalized monomer, N-[2-[2-(2-tert-butoxycarbonylaminooxyacetylamino-ethoxy)ethoxy]ethyl]-2-methacrylamide, which allows for the large-scale preparation of a versatile polymer characterized by its high stability, high blotting capacity, and easy use. The one-pot protocol allowed to profile 23 kinds of N-glycan chains of human serum glycoproteins. This concept was further applied for the glycopeptides analysis in a crude mixture followed by galactose oxidase treatment to generate free aldehyde group at the non-reducing terminal of oligosaccharide moiety of glycopeptides. Our technique may be implemented in existing biochemistry and molecular diagnostics laboratories because enriched oligosaccharides and glycopeptides by solid-phase transoximization with high-sensitive labeling reagents are widely applicable in a variety of common analytical methods using two-dimensional HPLC, LC/MS, and capillary electrophoresis as well as modern mass spectrometry.

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Some Aspects of Mechanism and Catalysis for Carbonyl Addition Reactions¹

Cited by 51 publications

References 6 publications

Kinetic and Structural Studies on the Catalytic Role of the Aspartic Acid Residue Conserved in Copper Amine Oxidase^,

Kinetic and Structural Studies on the Catalytic Role of the Aspartic Acid Residue Conserved in Copper Amine Oxidase^,

Glycosylation of aromatic amines II: Kinetics and mechanisms of the hydrolytic reaction between kynurenine and glucose

One‐Pot Solid‐Phase Glycoblotting and Probing by Transoximization for High‐Throughput Glycomics and Glycoproteomics

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Some Aspects of Mechanism and Catalysis for Carbonyl Addition Reactions1

Cited by 51 publications

References 6 publications

Kinetic and Structural Studies on the Catalytic Role of the Aspartic Acid Residue Conserved in Copper Amine Oxidase,

Kinetic and Structural Studies on the Catalytic Role of the Aspartic Acid Residue Conserved in Copper Amine Oxidase,

Glycosylation of aromatic amines II: Kinetics and mechanisms of the hydrolytic reaction between kynurenine and glucose

One‐Pot Solid‐Phase Glycoblotting and Probing by Transoximization for High‐Throughput Glycomics and Glycoproteomics

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Product

Resources

About

Some Aspects of Mechanism and Catalysis for Carbonyl Addition Reactions¹

Kinetic and Structural Studies on the Catalytic Role of the Aspartic Acid Residue Conserved in Copper Amine Oxidase^,

Kinetic and Structural Studies on the Catalytic Role of the Aspartic Acid Residue Conserved in Copper Amine Oxidase^,