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Thiol Peroxidase (thiol + peroxidase)

Distribution by Scientific Domains

Life Sciences	60%

Selected Abstracts

Comparative study of the physiological roles of three peroxidases (NADH peroxidase, Alkyl hydroperoxide reductase and Thiol peroxidase) in oxidative stress response, survival inside macrophages and virulence of Enterococcus faecalis

MOLECULAR MICROBIOLOGY, Issue 5 2007
Stephanie La Carbona
Summary The opportunistic pathogen Enterococcus faecalis is well equipped with peroxidatic activities. It harbours three loci encoding a NADH peroxidase, an alkyl hydroperoxide reductase and a protein (EF2932) belonging to the AhpC/TSA family. We present results demonstrating that ef2932 does encode a thiol peroxidase (Tpx) and show that it is part of the regulon of the hydrogen peroxide regulator HypR. Characterization of unmarked deletion mutants showed that all three peroxidases are important for the defence against externally provided H2O2. Exposure to internal generated H2O2 by aerobic growth on glycerol, lactose, galactose or ribose showed that Npr was absolutely required for aerobic growth on glycerol and optimal growth on the other substrates. Growth on glycerol was also dependent on Ahp. Addition of catalase restored growth of the mutants, and therefore, extracellular H2O2 concentrations have been determined. This showed that the time point of growth arrest of the ,npr mutant correlated with the highest H2O2 concentration measured. Analysis of the survival of the different strains inside peritoneal macrophages revealed that Tpx was the most important antioxidant activity for protecting the cells against the hostile phagocyte environment. Finally, the ,tpx and the triple mutant showed attenuated virulence in a mouse peritonitis model. [source]

Structure of the inactive variant C60S of Mycobacterium tuberculosis thiol peroxidase

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 5 2006
Matthias Stehr
The genome of Mycobacterium tuberculosis encodes several peroxiredoxins (Prxs) thought to be active against organic and inorganic peroxides. The open reading frame Rv1932 encodes a 165-residue thiol peroxidase (Tpx), which belongs to the atypical 2-Cys peroxiredoxin family. The crystal structure of the C60S mutant of M. tuberculosis Tpx (MtTpx) crystallized in space group P3121, with unit-cell parameters a = 106.08, b = 106.08, c = 65.33,Å. The structure has been refined to an R value of 17.1% (Rfree = 24.9%) at 2.1,Å resolution. MtTpx is structurally homologous to other peroxiredoxins, including the mycobacterial AhpC and AhpE. The inactive MtTpx C60S mutant structure closely resembles the structure of Streptococcus pneumoniae Tpx (SpTpx) and thus represents the reduced enzyme state. The mutated active-site serine is electrostatically linked to Arg130 and hydrogen bonded to Thr57, practically identical to the cysteine in SpTpx. A cocrystallized acetate molecule mimics the position of the substrate and interacts with Ser60, Arg130 and Thr57. [source]

Functional analysis and expression characteristics of chloroplastic Prx IIE

PHYSIOLOGIA PLANTARUM, Issue 3 2008
Filipe Gama
Peroxiredoxins (Prxs) are ubiquitous thiol-dependent peroxidases capable of eliminating a variety of peroxides through reactive catalytic cysteines, which are regenerated by reducing systems. Based on amino acid sequences and their mode of catalysis, five groups of thiol peroxidases have been distinguished in plants, and type II Prx is one of them with representatives in many sub-cellular compartments. The mature form of poplar chloroplastic Prx IIE was expressed as a recombinant protein in Escherichia coli. The protein is able to reduce H2O2 and tert-butyl hydroperoxide and is regenerated by both glutaredoxin (Grx) and thioredoxin (Trx) systems. Nevertheless, compared with Trxs, Grxs, and more especially chloroplastic Grx S12, are far more efficient reductants towards Prx IIE. The expression of Prx IIE at both the mRNA and protein levels as a function of organ type and abiotic stress conditions was investigated. Western blot analysis revealed that Prx IIE gene is constitutively expressed in Arabidopsis thaliana, mostly in young and mature leaves and in flowers. Under photo-oxidative treatment and water deficit, almost no change was observed in the abundance of Prx IIE in A. thaliana, while the level of Prx Q (one of the two other chloroplastic Prxs with 2-Cys Prx) increased in response to both stresses, indicating that plastidic members of the Prx family exhibit specific patterns of expression under stress. [source]