Zum Mechanismus der „frühen Phase”︁ der Maillard‐Reaktion 2. Mitt. Folgereaktionen von N‐Glycosiden

Westphal, G.; Kroh, Lothar W.

doi:10.1002/food.19850290809

Cited by 7 publications

(2 citation statements)

References 45 publications

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“…We further propose that the next step in the transformation of the covalently bound d-T6P to -d-galactofuranose 6-phosphate is a base-catalysed Heyns rearrangement (Westphal & Kroh, 1985;Wang, 2009;Fig. 7).…”

Section: Proposed Inhibition Mechanismmentioning

confidence: 99%

“…Heyns rearrangements describe the conversion of -hydroxy imines and Schiff bases into stable -amino carbonyl compounds via -hydroxyenamine intermediates (Wang, 2009). This reaction and the related Amadori rearrangement play important roles in conversions of -hydroxyamino sugars, for instance N-glycosides, in food chemistry (Westphal & Kroh, 1985). Abstraction of a proton from the C1 atom of the iminium intermediate by the negatively charged Tyr178 in TalB F178Y (Fig.…”

Section: Proposed Inhibition Mechanismmentioning

confidence: 99%

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Novel mode of inhibition byD-tagatose 6-phosphate through a Heyns rearrangement in the active site of transaldolase B variants

Stellmacher

Sandalova

Schneider

et al. 2016

Acta Cryst Sect D Struct Biol

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Transaldolase B (TalB) and D-fructose-6-phosphate aldolase A (FSAA) from Escherichia coli are C-C bond-forming enzymes. Using kinetic inhibition studies and mass spectrometry, it is shown that enzyme variants of FSAA and TalB that exhibit D-fructose-6-phosphate aldolase activity are inhibited covalently and irreversibly by D-tagatose 6-phosphate (D-T6P), whereas no inhibition was observed for wild-type transaldolase B from E. coli. The crystal structure of the variant TalB(F178Y) with bound sugar phosphate was solved to a resolution of 1.46 Å and revealed a novel mode of covalent inhibition. The sugar is bound covalently via its C2 atom to the ℇ-NH2 group of the active-site residue Lys132. It is neither bound in the open-chain form nor as the closed-ring form of D-T6P, but has been converted to β-D-galactofuranose 6-phosphate (D-G6P), a five-membered ring structure. The furanose ring of the covalent adduct is formed via a Heyns rearrangement and subsequent hemiacetal formation. This reaction is facilitated by Tyr178, which is proposed to act as acid-base catalyst. The crystal structure of the inhibitor complex is compared with the structure of the Schiff-base intermediate of TalB(E96Q) formed with the substrate D-fructose 6-phosphate determined to a resolution of 2.20 Å. This comparison highlights the differences in stereochemistry at the C4 atom of the ligand as an essential determinant for the formation of the inhibitor adduct in the active site of the enzyme.

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Section: Proposed Inhibition Mechanismmentioning

confidence: 99%

Section: Proposed Inhibition Mechanismmentioning

confidence: 99%

Novel mode of inhibition byD-tagatose 6-phosphate through a Heyns rearrangement in the active site of transaldolase B variants

Stellmacher

Sandalova

Schneider

et al. 2016

Acta Cryst Sect D Struct Biol

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Zum Mechanismus der „frühen Phase”︁ der Maillard‐Reaktion 1. Mitt. Einfluß der Struktur des Kohlenhydrats und der Aminosäure auf die Bildung des N‐Glycosids

Westphal

Kroh

1985

Nahrung

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Die Reaktion zwischen reduzierenden Kohlenhydraten und Aminokomponenten (Maillard‐Reaktion) kann über die Variation von inneren und äußeren Parametern kinetisch beeinflußt werden. Innere Parameter werden durch die Art und Struktur der Ausgangsstoffe, äußere Parameter durch Milieubedingungen wie pH‐Wert oder Temperatur bestimmt. Aus den experimentellen Befunden lassen sich zwanglos Aussagen zur Reaktivität der Zucker‐ und Amino‐komponente bezüglich der Maillard‐Reaktion ableiten. Vergleichende Untersuchungen an verschiedenen Modellsystemen Kohlenhydrat/DL‐Phenylalanin zeigten eine bevorzugte stereoselektive Reaktion der jeweiligen ß‐Anomeren. Neben dem Einfluß der Konformation der Kohlenhydrate sind auch die inneren Parameter Konstitution und Konfiguration der Aminokomponente für den Verlauf der nichtenzymatischen Bräunung von Bedeutung.

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Effect of Amadori rearrangement products on the non‐enzymic browning in model systems

Pokorný

Pilková

Davı́dek

et al. 1988

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The AMADORI product was prepared from D-glucose and L-alanine after HASHIBA. The browning process was investigated by determining the absorbance at 520 nm, in aqueous solutions at 110 "C for 5-8 h. Because of the limited access of oxygen and its low solubility in the reaction medium, the browning proceeded after zeroth order kinetics with the maximum browning rate at pH = 8-9. The browning rate remained unaffected by additions of sodium sulphite, rutin. propyl gallate (except when present at high levels), iron(I1l)chloride or copper(1I)chloride but decreased in presence of L-cysteine or iron(I1)chloride. Hydrogen peroxide bleached the pigment but did not inhibit the subsequent browning of reaction products. Under experimental conditions the solution of AMAWRI product did not darken with substantially greater rate than the solution of D-glucose and L-alanine. Lower additions of D-glucose to the solution of AMADON product moderately increased the reaction rate while additions of L-alanine or L-hydroxyproline moderately decreased the browning rate.

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Zum Mechanismus der „frühen Phase”︁ der Maillard‐Reaktion 2. Mitt. Folgereaktionen von N‐Glycosiden

Cited by 7 publications

References 45 publications

Novel mode of inhibition byD-tagatose 6-phosphate through a Heyns rearrangement in the active site of transaldolase B variants

Novel mode of inhibition byD-tagatose 6-phosphate through a Heyns rearrangement in the active site of transaldolase B variants

Zum Mechanismus der „frühen Phase”︁ der Maillard‐Reaktion 1. Mitt. Einfluß der Struktur des Kohlenhydrats und der Aminosäure auf die Bildung des N‐Glycosids

Effect of Amadori rearrangement products on the non‐enzymic browning in model systems

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