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Slow binding modulation of paraoxonase 1 activity with terbium ions
Janez Smerkolj1, Miha Bahun2, Nataša Poklar Ulrih2
1University of Ljubljana, Faculty of Medicine, Institute of Biochemistry and Molecular Genetics, Vrazov trg 2, 1000, Ljubljana, Slovenia.
Chemico-Biological Interactions
|August 18, 2025
Summary
Paraoxonase 1 (PON1) is a calcium-dependent enzyme. Terbium ions (Tb3+) act as slow-binding, reversible inhibitors of PON1
Area of Science:
- Biochemistry
- Enzymology
- Metalloprotein
Background:
- Paraoxonase 1 (PON1) is a calcium-dependent metalloenzyme crucial for hydrolyzing various substrates.
- Metal ions, particularly transition metals, can inhibit PON1 by binding to its surface residues.
- Lanthanide ions are known to interact with protein binding sites, potentially acting as potent PON1 inhibitors.
Purpose of the Study:
- To investigate the inhibitory effects of terbium ions (Tb3+) on recombinant PON1 (rePON1).
- To elucidate the mechanism by which Tb3+ binding modulates rePON1's enzymatic activity.
Main Methods:
- Characterization of recombinant PON1 (rePON1) activity.
- Kinetic analysis of Tb3+ inhibition on rePON1 lactonase activity.
- Investigation of the binding mechanism of Tb3+ to rePON1.
Main Results:
- Tb3+ ions were identified as slow-binding, reversible inhibitors of rePON1's lactonase activity.
- The inhibition follows a sequential, two-step mechanism.
- Tb3+ binding involves both catalytic and structural metal-binding sites of rePON1.
Conclusions:
- Tb3+ ions effectively inhibit PON1 activity through a specific, multi-step binding process.
- Understanding lanthanide inhibition provides insights into PON1's catalytic mechanism and metal ion interactions.
- This study clarifies the kinetic effects of lanthanides on PON1, highlighting their potential as modulators of enzyme function.
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