Catalases Are NAD(P)H-Dependent Tellurite Reductases

Iván L Calderón,Philip A Youderian,Claudia P Saavedra,Felipe A Arenas,Derie E Fuentes,Sergio E Pichuantes,Manuel A Araya,Juan C Tantaleán,Claudio C Vásquez,José Manuel Pérez,Christophe Herman

doi:10.1371/journal.pone.0000070

Iván L Calderón, Philip A Youderian + Show 9 more

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https://doi.org/10.1371/journal.pone.0000070

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Abstract

Reactive oxygen species damage intracellular targets and are implicated in cancer, genetic disease, mutagenesis, and aging. Catalases are among the key enzymatic defenses against one of the most physiologically abundant reactive oxygen species, hydrogen peroxide. The well-studied, heme-dependent catalases accelerate the rate of the dismutation of peroxide to molecular oxygen and water with near kinetic perfection. Many catalases also bind the cofactors NADPH and NADH tenaciously, but, surprisingly, NAD(P)H is not required for their dismutase activity. Although NAD(P)H protects bovine catalase against oxidative damage by its peroxide substrate, the catalytic role of the nicotinamide cofactor in the function of this enzyme has remained a biochemical mystery to date. Anions formed by heavy metal oxides are among the most highly reactive, natural oxidizing agents. Here, we show that a natural isolate of Staphylococcus epidermidis resistant to tellurite detoxifies this anion thanks to a novel activity of its catalase, and that a subset of both bacterial and mammalian catalases carry out the NAD(P)H-dependent reduction of soluble tellurite ion (TeO3 2−) to the less toxic, insoluble metal, tellurium (Te°), in vitro. An Escherichia coli mutant defective in the KatG catalase/peroxidase is sensitive to tellurite, and expression of the S. epidermidis catalase gene in a heterologous E. coli host confers increased resistance to tellurite as well as to hydrogen peroxide in vivo, arguing that S. epidermidis catalase provides a physiological line of defense against both of these strong oxidizing agents. Kinetic studies reveal that bovine catalase reduces tellurite with a low Michaelis-Menten constant, a result suggesting that tellurite is among the natural substrates of this enzyme. The reduction of tellurite by bovine catalase occurs at the expense of producing the highly reactive superoxide radical.

Highlights

Molecular oxygen accepts electrons to form the reduced derivatives superoxide radical and hydrogen peroxide, which damage living cells
To understand the biochemical basis for this resistance, we prepared cell-free extracts from S. epidermidis CH, and found that these extracts have an activity that catalyzes the reduction of K2TeO3, dependent on the presence of NADH (Fig. 1)
This activity is sensitive to heat, proteases, sodium dodecyl sulfate (SDS), and guanidine hydrochloride, arguing that it is due to the presence of an enzyme

Summary

Introduction

Molecular oxygen accepts electrons to form the reduced derivatives superoxide radical and hydrogen peroxide, which damage living cells. These reactive oxygen species and their products can modify nucleotide bases, cleave the phosphate backbone of DNA, crosslink proteins and lipids by free-radical driven chain reactions, and damage the active sites of critical enzymes. The monofunctional heme-containing catalases have been the subject of biochemical study for more than 100 years [3], and bovine liver catalase is among the first enzymes to be crystallized [4] It is among the few enzymes that have attained a catalytic efficiency equal to that limited by the rate of diffusion of its substrate, hydrogen peroxide. Many catalases have been shown to be peroxidases, and can oxidize short-chain alcohols including ethanol and other substrates in a two-step reaction dependent on hydrogen peroxide [6,7,8]

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