title: A comparison of thiol peroxidase mechanisms.
abstract: Thiol peroxidases comprise glutathione peroxidases (GPx) and peroxiredoxins (Prx). The enzymes of both families reduce hydroperoxides with thiols by enzyme-substitution mechanisms. H(2)O(2) and organic hydroperoxides are reduced by all thiol peroxidases, most efficiently by SecGPxs, whereas fast peroxynitrite reduction is more common in Prxs. Reduction of lipid hydroperoxides is the domain of monomeric GPx4-type enzymes and of some Prxs. The catalysis starts with oxidation of an active-site selenocysteine (U(P)) or cysteine (C(P)). Activation of Cys (Sec) for hydroperoxide reduction in the GPx family is achieved by a typical tetrad composed of Cys (Sec), Asn, Gln, and Trp, whereas a triad of Cys Thr (or Ser) and Arg is the signature of Prx. In many of the CysGPxs and Prxs, a second Cys (C(R)) is required. In these 2-CysGPxs and 2-CysPrxs, the C(P) oxidized to a sulfenic acid forms an intra- or intermolecular disulfide (typical 2-CysPrx) with C(R), before a stepwise regeneration of ground-state enzyme by redoxin-type proteins can proceed. In SecGPxs and sporadically in Prxs, GSH is used as the reductant. Diversity combined with structural variability predestines thiol peroxidases for redox regulation via ROOH sensing and direct or indirect transduction of oxidant signals to specific protein targets.
authors.affiliation: Otto-von-Guericke-Universität and MOLISA GmbH, Magdeburg, Germany. l.flohe@t-online.de
authors.forename: Leopold
authors.initials: L
authors.lastname: Flohé
authors.forename: Stefano
authors.initials: S
authors.lastname: Toppo
authors.forename: Giorgio
authors.initials: G
authors.lastname: Cozza
authors.forename: Fulvio
authors.initials: F
authors.lastname: Ursini
mesh_terms: D002384:Catalysis; D020134:Catalytic Domain; D003545:Cysteine / Q000737:chemistry; D005979:Glutathione Peroxidase / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry; D010084:Oxidation-Reduction; D054464:Peroxiredoxins / Q000737:chemistry*; D030421:Peroxynitrous Acid / Q000737:chemistry; D011487:Protein Conformation; D017279:Selenocysteine / Q000737:chemistry; D015398:Signal Transduction; D013438:Sulfhydryl Compounds / Q000737:chemistry*
chemical_list: D013438:Sulfhydryl Compounds; D017279:Selenocysteine; D030421:Peroxynitrous Acid; D006861:Hydrogen Peroxide; D054464:Peroxiredoxins; D005979:Glutathione Peroxidase; D003545:Cysteine