Secondary deuterium kinetic isotope effects in the cleavage of thiamin and N-methylthiaminium ion: first evidence to identify the rate-limiting step

1989 ◽  
Vol 54 (16) ◽  
pp. 3941-3945 ◽  
Author(s):  
Georg Uray ◽  
Claude Celotto ◽  
Anton Ibovnik ◽  
John A. Zoltewicz
Keyword(s):  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Kinetic Isotope ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting

scholarly journals Comment on “Topography of the free energy landscape of Claisen–Schmidt condensation: solvent and temperature effects on the rate-controlling step” by N. D. Coutinho, H. G. Machado, V. H. Carvalho-Silva and W. A. da Silva, Phys. Chem. Chem. Phys., 2021, 23, 6738

2021 ◽  
Vol 23 (38) ◽  
pp. 22199-22201
Author(s):  
Charles L. Perrin
Keyword(s):  
Temperature Effects ◽  
Isotope Effects ◽  
Energy Landscape ◽  
Kinetic Isotope Effects ◽  
Chem Phys ◽  
Kinetic Isotope ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting ◽  
Rate Controlling Step

The referenced article in PCCP presents calculations of solvent kinetic isotope effects that indicate that the rate-limiting step in base-catalyzed chalcone formation in aqueous solution becomes the second enolization.

Kinetic Isotope Effects on the Rate-Limiting Step of Heme Oxygenase Catalysis Indicate Concerted Proton Transfer/Heme Hydroxylation

2003 ◽  
Vol 125 (52) ◽  
pp. 16208-16209 ◽  
Author(s):  
Roman Davydov ◽  
Toshitaka Matsui ◽  
Hiroshi Fujii ◽  
Masao Ikeda-Saito ◽  
Brian M. Hoffman
Keyword(s):  
Proton Transfer ◽  
Heme Oxygenase ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Kinetic Isotope ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting

Ligand-Accelerated Non-Directed C–H Cyanation of Arenes

2018 ◽  
Author(s):  
Luoyan Liu ◽  
Kap-Sun Yeung ◽  
jin-quan yu
Keyword(s):  
Natural Products ◽  
Bond Cleavage ◽  
Drug Molecules ◽  
Kinetic Isotope ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Broad Scope ◽  
Synthetic Utility ◽  
Rate Limiting

<p>We herein report the first example of a 2-pyridone accelerated non-directed C−H cyanation with an arene as the limiting reagent. This protocol is compatible with a broad scope of arenes, including advanced intermediates, drug molecules, and natural products. A kinetic isotope experiment (k<sub>H</sub>/k<sub>D</sub> = 4.40) indicates that the C–H bond cleavage is the rate-limiting step. Also, the reaction is readily scalable, further showcasing the synthetic utility of this method.<i></i></p>

scholarly journals Kinetic isotope effects of peptidylglycine α-hydroxylating mono-oxygenase reaction

1998 ◽  
Vol 336 (1) ◽  
pp. 131-137 ◽  
Author(s):  
Kenichi TAKAHASHI ◽  
Tetsuo ONAMI ◽  
Masato NOGUCHI
Keyword(s):  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Tracer Method ◽  
Deuterium Isotope Effect ◽  
Critical Determinant ◽  
Product Release ◽  
Kinetic Isotope ◽  
Hydroxylation Reaction ◽  
Double Label ◽  
Rate Limiting

Many bioactive polypeptides or neuropeptides possess a C-terminal α-amide group as a critical determinant for their optimal bioactivities. The amide functions are introduced by the sequential actions of peptidylglycine α-hydroxylating mono-oxygenase (PHM; EC 1.14.17.3) and peptidylamidoglycollate lyase (PAL; EC 4.3.2.5) from their glycine-extended precursors. In the present study we examined the kinetic isotope effects of the frog PHM reaction by competitive and non-competitive approaches. In the competitive approach we employed the double-label tracer method with d-Tyr-[U-14C]Val-Gly, d-Tyr-[3,4-3H]Val-[2,2-2H2]-Gly, and d-Tyr-Val-(R,S)[2-3H]Gly as substrates, and we determined the deuterium and tritium effects on Vmax/Km as 1.625±0.041 (mean±S.D.) and 2.71±0.16 (mean±S.D.), respectively. The intrinsic deuterium isotope effect (Dk) on the glycine hydroxylation reaction was estimated to be 6.5–10.0 (mean 8.1) by the method of Northrop [Northrop (1975) Biochemistry 14, 2644–2651]. In the non-competitive approach with N,N-dimethyl-1,4-phenylenediamine as a reductant, however, the deuterium effect on Vmax (DV) was approximately unity, although the deuterium effect on Vmax/Km (DV/K) was comparable to that obtained by the competitive approach. These results indicated that DV was completely masked by the presence of one or more steps much slower than the glycine hydroxylation step and that DV/K was diminished from Dk by a large forward commitment to catalysis. The addition of PAL, however, increased the apparent DV from 1.0 to 1.2, implying that the product release step was greatly accelerated by PAL. These results suggest that the product release is rate-limiting in the overall PHM reaction. The large Dk indicated that the glycine hydroxylation catalysed by PHM might proceed in a stepwise mechanism similar to that proposed for the dopamine β-hydroxylase reaction [Miller and Klinman (1983) Biochemistry 22, 3091–3096].

scholarly journals Path Integral Calculation of the Hydrogen/Deuterium Kinetic Isotope Effect in Monoamine Oxidase A-Catalyzed Decomposition of Benzylamine

Molecules ◽  
2019 ◽  
Vol 24 (23) ◽  
pp. 4359 ◽  
Author(s):  
Mateusz Z. Brela ◽  
Alja Prah ◽  
Marek Boczar ◽  
Jernej Stare ◽  
Janez Mavri
Keyword(s):  
Monoamine Oxidase ◽  
Isotope Effect ◽  
Path Integral ◽  
Kinetic Isotope Effect ◽  
Monoamine Oxidase A ◽  
Kinetic Isotope ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Hydrogen Deuterium ◽  
Rate Limiting

Monoamine oxidase A (MAO A) is a well-known enzyme responsible for the oxidative deamination of several important monoaminergic neurotransmitters. The rate-limiting step of amine decomposition is hydride anion transfer from the substrate α–CH2 group to the N5 atom of the flavin cofactor moiety. In this work, we focus on MAO A-catalyzed benzylamine decomposition in order to elucidate nuclear quantum effects through the calculation of the hydrogen/deuterium (H/D) kinetic isotope effect. The rate-limiting step of the reaction was simulated using a multiscale approach at the empirical valence bond (EVB) level. We applied path integral quantization using the quantum classical path method (QCP) for the substrate benzylamine as well as the MAO cofactor flavin adenine dinucleotide. The calculated H/D kinetic isotope effect of 6.5 ± 1.4 is in reasonable agreement with the available experimental values.

Experimental and Theoretical Kinetic Isotope Effects for Asymmetric Dihydroxylation. Evidence Supporting a Rate-Limiting “(3 + 2)” Cycloaddition

1997 ◽  
Vol 119 (41) ◽  
pp. 9907-9908 ◽  
Author(s):  
Albert J. DelMonte ◽  
Jan Haller ◽  
K. N. Houk ◽  
K. Barry Sharpless ◽  
Daniel A. Singleton ◽  
...  
Keyword(s):  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Asymmetric Dihydroxylation ◽  
Kinetic Isotope ◽  
Rate Limiting
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