Which glycoside is an enzyme inhibitor

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Title:Assay development and inhibitor synthesis for the trans-sialidase from Trypanosoma cruziOther titles:Assay development and inhibitor synthesis for the trans-sialidase from Trypanosoma cruziLanguage:GermanAuthor:Meinke, SebastianTags:Affinity measurement; C-glycosides; Trans-sialidase; chagas disease; trans-sialidase; inhibitors; c-glycosides; cross metathesisGND keywords:Chagas disease; Acetylneuraminic acid ; Preparative organic chemistry; Immobilized enzyme; Enzyme inhibitor; Surface plasmon resonancePublication date:2010Day of the oral exam:2010-05-07Summary:
Trypanosoma cruzi trans-sialidase (TcTS) is a key enzyme in the pathogenesis
South American trypanomiasis, Chagas disease. With the help of this enzyme
The pathogens causing the disease transfer sialic acid residues from host cells to their own
Cell surface glycans. This process is for the cell invasion of the trypanosomes
indispensable, which is why TcTS is a suitable starting point for the development of new
Therapies for Chagas disease is.
In this work, new C-glycosidic
N-acetylneuraminic acid derivatives as potential inhibitors or modulators of enzyme activity
synthesized. The fact that the opposite of the
Hydrolysis of sialosides preferential transsialylation in TcTS for the presence of a
Binding site for the acceptor substrate formed from two aromatic amino acids
(acceptor binding site).
The binding to the acceptor binding site was made in the newly synthesized ligand
aromatic residues brought about the hydrophobic interaction through π interactions
should mimic the galactosides with the aromatic amino acids. For it played as
Synthesis method mainly the ruthenium-catalyzed cross metathesis of allyl glycosides
with styrene derivatives but also with olefinic carbohydrate residues play a role.
SPR binding studies confirmed the effectiveness of this design: the presence of one
aromatic residue in the C-glycoside of N-acetylneuraminic acid leads to a millimolar
Dissociation constant, while the α-allyl-C-glycoside does not bind without an aromatic residue.
An NMR-based reaction monitoring of the TcTS-catalyzed sialylation of methylallolactoside
with p-nitrophenylsialoside (pNP-Neu5Ac) showed the influence of the ligand with
the highest affinity for enzymatic activity: a 1 millimolar concentration of the
Ligands resulted in a 44% decrease in enzymatic activity.
The new structure of the ligands and those with good yields in just a few steps
feasible synthesis offers an approach for further investigation. In particular with the
Cross metathesis is through the use of different unsaturated reactants
the construction of ligand libraries possible.
Such as the synthesis of a C-glycosidic α, 2-6-sialyllactose analogue in this work
shows is the application of the synthetic route shown to the development of ligands
for other targets easily possible.

The trans-sialidase of Trypanosoma cruzi (TcTS) is a key enzyme in the pathogenesis of the
South American trypanomiasis, Chagas disease. Utilizing this enzyme for the pathogen transfers
sialic acid from host cells to its own cell surface glycans. This process is essential for the host cell
invasion, thus TcTS is a convenient target for the development of new treatments for Chagas
disease.
In this thesis new C-glycosidic derivatives of sialic acid were synthesized as potential
inhibitors or modulators of enzyme activity, based on the known crystal structure of TcTS.
The main goal was to address the acceptor binding site, composed of two aromatic amino acid residues.
Binding to the acceptor binding site was accomplished by including aromatic residues in the newly synthesized
ligands. The synthetic method of choice was primarily the ruthenium catalyzed cross metathesis of allyl
C-glycosides with derivatives of styrene and sugar olefins.
Binding studies by SPR confirmed the efficacy of this approach: presence of an aromatic
residue in the C-sialoside resulted in a millimolar dissociation constant whereas the α-allyl C-sialoside
lacking an aromatic residue exhibited no binding at all.
A NMR based measurement of substrate conversion applying the TcTS catalyzed reaction of
p-nitrophenyl sialoside with methyl allolactoside revealed the influence of the best ligand on
enzymatic activity: presence of the ligand (1 mM) in the reaction mixture resulted in a 44%
loss of enzyme activity.
The new design of ligands and the facile synthesis featuring high yields in few steps present
an attractive perspective for further investigations. Establishing a ligand library by applying
the cross metathesis protocol to a variety of unsaturated reagents could be a straightforward
attempt to optimize ligands and find low concentration inhibitors for TcTS. As shown by the
synthesis of a C-glycosidically linked α, 2-6-sialyl lactose analogue, the application of the
synthetic pathway to the development of ligands for targets other than TcTS is also a
promising task.
Url:https://ediss.sub.uni-hamburg.de/handle/ediss/3664URN:urn: nbn: de: gbv: 18-46165Document type:dissertationSupervisor:Thiem, Joachim (Prof. Dr.)Included in the collections:Electronic dissertations and habilitations