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Catalases are NAD(P)H-dependent tellurite reductases
Iván L Calderón1, Felipe A Arenas, José Manuel Pérez
1Laboratorio de Microbiología Molecular, Facultad de Química y Biología, Universidad de Santiago de Chile, Santiago, Chile.
Plos One
|December 22, 2006
Summary
Catalases defend against reactive oxygen species and hydrogen peroxide. This study reveals a novel NAD(P)H-dependent activity where catalases reduce toxic tellurite to elemental tellurium, offering new insights into cellular defense mechanisms.
Area of Science:
- Biochemistry
- Enzymology
- Cellular Biology
Background:
- Reactive oxygen species (ROS) cause cellular damage, contributing to diseases like cancer and aging.
- Catalases are crucial enzymes that neutralize hydrogen peroxide, a major ROS.
- The role of nicotinamide cofactors (NAD(P)H) in catalase function, beyond peroxide dismutation, remained unclear.
Purpose of the Study:
- To investigate a novel enzymatic activity of catalases beyond peroxide detoxification.
- To explore the role of catalases in the detoxification of heavy metal anions, specifically tellurite.
- To elucidate the NAD(P)H-dependent mechanism of tellurite reduction by catalases.
Main Methods:
- Enzyme kinetics assays using bovine and bacterial catalases.
- In vitro reduction assays of tellurite ion (TeO(3)(2-)) to elemental tellurium (Te(o)).
- Heterologous expression of Staphylococcus epidermidis catalase in Escherichia coli to assess tellurite and hydrogen peroxide resistance.
Main Results:
- Staphylococcus epidermidis catalase confers resistance to both tellurite and hydrogen peroxide in vivo.
- Bacterial and mammalian catalases exhibit NAD(P)H-dependent reduction of tellurite to tellurium.
- Bovine catalase efficiently reduces tellurite, suggesting it as a natural substrate, with superoxide radical production as a byproduct.
Conclusions:
- Catalases possess a previously unrecognized NAD(P)H-dependent activity for detoxifying tellurite.
- This novel catalase function provides a cellular defense against both hydrogen peroxide and tellurite exposure.
- The findings expand our understanding of catalase enzymatic capabilities and their role in mitigating heavy metal toxicity.
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