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Updated: Oct 25, 2025
08:31
Anaerobic Protein Purification and Kinetic Analysis via Oxygen Electrode for Studying DesB Dioxygenase Activity and Inhibition
Published on: October 3, 2018
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Emerging roles for thiol dioxygenases as oxygen sensors
Dona M Gunawardana1, Karen C Heathcote1, Emily Flashman1
1Department of Chemistry, University of Oxford, UK.
The FEBS Journal
|August 4, 2021
Summary
Thiol dioxygenases (TDOs) and N-terminal cysteinyl dioxygenase enzymes (NCOs) are Fe(II)-dependent enzymes. Structural differences may explain NCOs
Area of Science:
- Biochemistry
- Enzymology
- Structural Biology
Background:
- Thiol dioxygenases (TDOs) are Fe(II)-dependent enzymes catalyzing thiol oxidation to sulfinates, sharing a cupin fold and 3xHis metal-coordinating triad.
- N-terminal cysteinyl dioxygenase enzymes (NCOs), including plant cysteine oxidases (PCOs) and human 2-aminoethanethiol dioxygenase (ADO), represent a distinct subclass.
- ADO functions as both an NCO and a small molecule TDO, while PCOs and ADO act as oxygen (O2) sensors regulating target protein stability via the N-degron pathway.
Purpose of the Study:
- To discuss the structural features differentiating TDOs and NCOs.
- To explore how structural variations influence substrate binding (small molecules vs. polypeptides) and O2 sensing capabilities in NCOs.
- To understand enzyme-substrate interactions, including O2, for potential therapeutic and adaptive strategies.
Main Methods:
- Comparative analysis of structural features between TDOs and NCOs.
- Kinetic analyses of NCOs' enzymatic activity.
- Investigation of hypoxic regulation of biological targets.
Main Results:
- While NCOs conserve the cupin fold and 3xHis triad, they exhibit distinct active site features and protein architecture compared to small molecule TDOs.
- Evidence suggests PCOs and ADO function as O2 sensors, with oxidation of N-terminal cysteine triggering protein degradation.
- Structural differences are proposed to dictate substrate specificity and O2 sensing mechanisms in NCOs.
Conclusions:
- NCOs represent a divergent subclass of TDOs with unique structural adaptations.
- These structural features are critical for substrate recognition and oxygen sensing.
- Understanding these enzymes offers potential for manipulating activity in hypoxic diseases and plant responses to environmental stress.
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