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Bio-layer Interferometry for Measuring Kinetics of Protein-protein Interactions and Allosteric Ligand Effects
Published on: February 18, 2014
Substrate-dependent modulation of enzyme activity by allosteric effector antibodies
John N Barlow1, Katja Conrath, Jan Steyaert
1Structural Biology, Free University of Brussels, Brussels, Belgium. jbarlow@vub.ac.be
Biochimica Et Biophysica Acta
|April 8, 2009
Summary
Antibody variable domain fragments (VHH domains) act as allosteric effectors for Trypanosoma vivax nucleoside hydrolase (TvNH). These VHH domains can either stimulate or inhibit enzyme activity, depending on the specific substrate.
Area of Science:
- Biochemistry
- Enzymology
- Structural Biology
Background:
- Trypanosoma vivax nucleoside hydrolase (TvNH) is a key enzyme in parasite metabolism.
- Antibody variable domain fragments (VHH domains) derived from camelid heavy-chain-only antibodies offer unique therapeutic potential.
- Allosteric regulation of enzyme activity is a critical mechanism in biological systems.
Purpose of the Study:
- To investigate the kinetic effects of VHH domains as allosteric effectors on TvNH activity.
- To elucidate the substrate-dependent modulation of TvNH by VHH domains.
- To explore the potential of VHH domains as drug development tools against parasitic infections.
Main Methods:
- Steady-state and pre-steady-state kinetic experiments were employed.
- Kinetic parameters such as kcat and Km were determined for TvNH with different substrates.
- The binding of VHH domains and their impact on catalytic steps were analyzed.
Main Results:
- VHH domains were found to act as potent allosteric effectors of TvNH, either stimulating or inhibiting its activity.
- The VHH domain 1589 demonstrated substrate-dependent effects, altering the rates of specific catalytic steps like N-glycosidic bond cleavage and product release.
- For 7-methyl guanosine, VHH 1589 increased kcat by accelerating product release; for pNPR, it decreased kcat and kcat/Km by making chemistry rate-determining.
Conclusions:
- The substrate-dependent kinetic effects of VHH domains on TvNH are attributed to alterations in the relative rates of catalytic steps.
- VHH domains can selectively modulate enzyme activity by targeting different steps in the catalytic pathway.
- These findings highlight the potential of VHH domains as versatile allosteric effectors for therapeutic intervention, particularly in parasitic diseases.
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