Review Cite This: Chem. Rev. 2019, 119, 10829−10855 pubs.acs.org/CR Catalysis of Peroxide Reduction by Fast Reacting Protein Thiols Focus Review †,‡ †,‡ ‡,§ ‡,§ ∥ Ari Zeida, Madia Trujillo, Gerardo Ferrer-Sueta, Ana Denicola, Darío A. Estrin, and Rafael Radi*,†,‡ † ‡ § Departamento de Bioquímica, Centro de Investigaciones Biomedicaś (CEINBIO), Facultad de Medicina, and Laboratorio de Fisicoquímica Biologica,́ Facultad de Ciencias, Universidad de la Republica,́ 11800 Montevideo, Uruguay ∥ Departamento de Química Inorganica,́ Analítica y Química-Física and INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, 2160 Buenos Aires, Argentina ABSTRACT: Life on Earth evolved in the presence of hydrogen peroxide, and other peroxides also emerged before and with the rise of aerobic metabolism. They were considered only as toxic byproducts for many years. Nowadays, peroxides are also regarded as metabolic products that play essential physiological cellular roles. Organisms have developed efficient mechanisms to metabolize peroxides, mostly based on two kinds of redox chemistry, catalases/peroxidases that depend on the heme prosthetic group to afford peroxide reduction and thiol-based peroxidases that support their redox activities on specialized fast reacting cysteine/selenocysteine (Cys/Sec) residues. Among the last group, glutathione peroxidases (GPxs) and peroxiredoxins (Prxs) are the most widespread and abundant families, and they are the leitmotif of this review. After presenting the properties and roles of different peroxides in biology, we discuss the chemical mechanisms of peroxide reduction by low molecular weight thiols, Prxs, GPxs, and other thiol-based peroxidases. Special attention is paid to the catalytic properties of Prxs and also to the importance and comparative outlook of the properties of Sec and its role in GPxs. To finish, we describe and discuss the current views on the activities of thiol-based peroxidases in peroxide-mediated redox signaling processes. CONTENTS 5.2. The Redox-Relay Model 10844 6. Conclusions and Perspectives 10845 1. Introduction 10829 Author Information 10845 2. Peroxides in Biology 10830 Corresponding Author 10845 2.1. Hydrogen Peroxide 10830 ORCID 10845 2.2. Peroxymonocarbonate 10830 Notes 10845 2.3. Peroxynitrous Acid 10831 Downloaded via UNIV DE BUENOS AIRES on March 3, 2020 at 13:35:56 (UTC). Biographies 10845 2.4. Lipid Hydroperoxides 10831 Acknowledgments 10846 2.5. Other Hydroperoxides 10831 References 10846 See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles. 3. Reduction of Hydroperoxides by Thiols 10831 3.1. Reactivity with Low Molecular Weight Thiols 10832 4. Cysteine-Based Peroxidases 10833 4.1. Peroxiredoxins 10834 1. INTRODUCTION 4.1.1. Mechanism of Catalysis 10835 For many years, peroxides in biology were considered toxic 4.2. Glutathione Peroxidases 10838 byproducts of aerobic metabolism. These peroxides include 4.2.1. Cysteine versus Selenocysteine in Per- hydrogen peroxide (H O ), peroxynitrous acid (ONOOH), and oxidases 10839 2 2 organic hydroperoxides (such as lipid hydroperoxides). Along 4.2.2. Catalytic Mechanism of Hydroperoxide the evolution, organisms developed efficient systems to reduce Reduction by Glutathione Peroxidases 10839 toxic peroxides. The biological function of peroxides was 4.3. Other Examples of Protein Thiols Prone to thought to be confined to cells of the immune system to fight Oxidation by Hydroperoxides 10841 against pathogen invasion. Even in these cells, after the infection 4.4. Comments on Hydroperoxide Specificities 10841 is controlled, inflammation needs to be resolved and again, the 4.5. Limitations of Comparing Low Molecular levels of peroxides need to be decreased. In aerobic organisms, Weight Thiols and Protein Thiol Reactivity 10842 5. Redox Signaling by Thiol Peroxidases 10843 5.1. The Floodgate Model 10844 Received: June 11, 2019 Published: September 9, 2019 © 2019 American Chemical Society 10829 DOI: 10.1021/acs.chemrev.9b00371 Chem. Rev. 2019, 119, 10829−10855 Chemical Reviews Review an enzyme specialized to eliminate hydrogen peroxide was addition, several members of the NOX family expressed in fi found rst: catalase, in general included in organelles specialized nonphagocytic cells produce H2O2 (either directly or through 1,2 ff •− ff for that task, the peroxisomes. Catalase e ectively dispropor- O2 dismutation) in response to di erent signaling molecules tionates H O into water and oxygen and has a very large including growth factors and cytokines.21 Mitochondria are also 2 2 •− turnover number. The mechanism of catalysis of H2O2 important sources of O2 that after Mn superoxide dismutase 22−24 elimination depends on the heme group of the enzyme, which (SOD)-catalyzed dismutation form H2O2. Superoxide can 25 is also present in other peroxidases such as ascorbate peroxidase. be reduced to H2O2 either nonenzymatically or in reactions Adifferent peroxidase activity was detected in red blood cells catalyzed by superoxide reductases (SOR) expressed in some in 19573 and later characterized as a selenoprotein in the early bacteria.26,27 Finally, H O can also be formed from the direct − 2 2 1970s, as the classical glutathione peroxidase (GPxs).4 6 GPxs two-electron reduction of oxygen catalyzed by oxidases present possess a particular amino acid residue, a selenocysteine (Sec) in different cellular compartments or in the extracellular space, that specifically reacts with peroxides with high rate constants (k such as xanthine oxidase and amino acid oxidases, among − ∼ 105−107 M−1 s−1) and is oxidized to selenenic acid. The others.28 32 enzyme is reduced back by two consecutive reactions with H O can permeate biological membranes, in a process that is 2 2 − glutathione (GSH) with the formation of a mixed selenenylsul- facilitated and regulated by specific aquaporin isoforms.33 36 fi °′ 37 de intermediate. With E (H2O2,H2O) = 1.349 V, H2O2 is a strong oxidant but More recently, enzymes first described as thiol-specific kinetic barriers limit its reactivity mostly to thiol-, selenol-, or antioxidants (TSA), and later named peroxiredoxins (Prxs), heme-dependent peroxidases and a few other transition metal 20 were found to be capable of reducing peroxides using only one or centers. The former reactions are in the basis of H2O2- two cysteine (Cys) residues (no heme, and no Sec is required) dependent redox signaling (see section 4), while reaction with − and a reducing substrate such as thioredoxin (Trx).7 10 [The some reduced transition metal centers may promote the IUBMB enzyme nomenclature committee acknowledges several formation of the highly oxidant hydroxyl radical (•OH) or − abbreviations for referring to peroxiredoxins (https://www. metal-oxo complexes through Fenton chemistry.38 40 •OH is a qmul.ac.uk/sbcs/iubmb/enzyme/EC1/11/1/15.html), Prx and nonspecific oxidant due to its extremely high reactivity and PRDX being the most widely used.] They are very abundant in corresponding short half-life (<μs). However, it is worth noting most organisms and cell compartments. Because the peroxidatic that localized generation of •OH, resulting from the reaction Cys residue of Prxs (CP) reacts with peroxides with rate with either metal binding to DNA or from the presence of constants in the 104−108 M−1 s−1 range, Prxs are able to detect reduced transition metal cofactors in proteins, promotes site- very low levels of peroxides, act as sensors and, importantly, specific DNA damage41 or selective one-electron amino acid provide specificity to the signaling process through particular oxidation.42 protein−protein interactions. Indeed, these thiol peroxidases are 2.2. Peroxymonocarbonate not only implicated in directly decreasing the levels of peroxides − The equilibrium of H O with CO /HCO forms peroxymo- to diminish oxidative damage but also in regulating redox 2 −2 2− 3 signaling toward adaptive response to oxidative stress.11 In nocarbonate (HOOCO2 or HCO4 , reaction R1), which is an anion at physiological pH.43,44 Kinetic and mechanistic analysis addition to Prxs, other peroxidases that depend on thiols for − indicate that HCO4 formation involves CO2 and either H2O2 catalysis have been described, such as thiol-based GPx and −1 −1 − −1 12,13 (k = 0.02 M s ) or its conjugate base, HOO (k = 280 M organic hydroperoxide resistance protein (Ohr). −1 43 In this review, we will focus on the mechanisms of catalysis of s ) as the reactive species, i.e., it is a perhydration reaction. hydroperoxide reduction by thiols with special emphasis on the From the pKa of H2O2 and the rate constants mentioned above, it was calculated that both pathways contribute ∼60% and 40%, specialized protein thiols such as the peroxidatic Cys of Prxs. − 45 respectively, to HCO4 formation at pH 7.4. −− 2. PEROXIDES IN BIOLOGY HCO32242++ H OV HCO H O (R1) −1 ° According to the IUPAC Gold Book (https://goldbook.iupac. The reported Keq of reaction R1 (0.33 M at 25 C) and the − −1 −1 org/html/H/H02905.html), hydroperoxides are monosubstitu- slow kapp of HCO4 formation (0.034 M s at pH 7.4) in tion products of hydrogen peroxide (HOOH, or H2O2) having comparison with those of other biologically relevant targets of 14 the ROOH skeleton, in which R is any organyl group. Through H2O2 caused this route not be considered of biological relevance this review, however, we preferred to utilize the term unless accelerated by carbonic anhydrase or by protein or lipid 45 hydroperoxide in a broader sense, to include H2O2 itself as environments.