Kinetic study on the cis-trans isomerization of peptidyl-proline dipeptides

Thunecke, Frank; Kálmán, András; Kálmán, Franka; Ma, Stacey; Rathore, Anurag S.; Horváth, Csaba

doi:10.1016/0021-9673(96)00241-5

Cited by 49 publications

(47 citation statements)

References 28 publications

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“…1). Such differences in cis/trans ratios between ad hoc solutions and equilibrated solutions have already been described for natural Xaa-Pro dipeptide conformers (16). The evidently low interconversion rate of Ala-[CS-N]-Pro isomers, which enabled the following experiments to be done, was confirmed by monitoring the cis/trans ratio changes after dissolution using HPCE.…”

Section: Cis/trans Ratio Of Ala-[cs-n]-pro-bothmentioning

confidence: 66%

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Evidence for the Absolute Conformational Specificity of the Intestinal H+/Peptide Symporter, PEPT1

Brandsch¹,

Thunecke²,

Küllertz³

et al. 1998

Journal of Biological Chemistry

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This study was initiated to determine whether the intestinal H؉ /peptide symporter PEPT1 differentiates between the peptide bond conformers of substrates. We synthesized a modified dipeptide where the peptide bond is replaced by the isosteric thioxo peptide bond. The Ala-Pro derivative Ala-[CS-N]-Pro exists as a mixture of cis and trans conformation in aqueous solution and is characterized by a low cis/trans isomerization rate. The compound was recognized by PEPT1 with high affinity. The K i value of Ala-[CS-N]-Pro for the inhibition of the uptake of radiolabeled glycylsarcosine in Caco-2 cells was 0.30 ؎ 0.02 mM, determined in solution with 96% trans conformation. In contrast, the K i value was 0.51 ؎ 0.02 mM when uptake media with 62% trans conformer were used. We conclude that only the trans conformer interacts with the transport system. From our data, a significant affinity of the cis conformer at PEPT1 cannot be derived. In a second approach, conformer-specific uptake of Ala-[CS-N]-Pro was studied by analyzing the intracellular content of Caco-2 cells following transport as well as the composition of the extracellular medium using capillary electrophoresis. The percentage of trans conformer that was 62% in the uptake medium increased to 92% inside the cells. This is the first direct evidence that an H ؉

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Section: Cis/trans Ratio Of Ala-[cs-n]-pro-bothmentioning

confidence: 66%

“…1 HPCE and NMR Analyses-HPCE analysis was performed using a BioFocus 3000 (Bio-Rad, Germany) (14,16). UV detection was done at 270 nm where Ala-[CS-N]-Pro shows maximal absorption.…”

Section: Synthesis Of Ala-[cs-n]-pro-mentioning

confidence: 99%

Evidence for the Absolute Conformational Specificity of the Intestinal H+/Peptide Symporter, PEPT1

Brandsch¹,

Thunecke²,

Küllertz³

et al. 1998

Journal of Biological Chemistry

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“…With these approaches, Horvath and co-workers [21] were able to use CE to calculate the rate constants for the reversible interconversion of Phe-Pro at 1.5, 4.0, and 107C. Reported values of k f (cis ?…”

Section: Damkohler Analysismentioning

confidence: 99%

“…In 1995, Horvath and co-workers [20,21] introduced Damkohler analysis as the first method used to estimate firstorder rate constants analytically from CE. The general pre-mise of this method rests upon the presumption that molecules undergoing reversible, first-order reactions are separable, and that the areas of the reactive zone are representative of predominantly species A and B molecules (Eq.…”

Section: Damkohler Analysismentioning

confidence: 99%

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Advances in CE for kinetic studies

Newman

Collins

2007

Electrophoresis

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CE is a promising technique for the investigation of molecular interactions because it affords evaluation of multiple interaction modes, does not require immobilization of molecules, and has no dead time. In order to perform these investigations, numerous methods have been developed for determining binding constants and other thermodynamic parameters. These methods have been reviewed extensively in recent years. However, methods for determining the rates of reaction are less prolific. Nonetheless, numerous theoretical and experimental advances have been made in recent years to address this discrepancy. Some of these methods employ computer simulations to determine first-order or second-order rate constants numerically, whereas other methods calculate rate constants directly as solutions to analytical equations. It is the object of this review to provide descriptions of these methods in terms of their underlying assumptions, experimental methodology, calculation of rate constants, and inherent limitations.

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