English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Single and double site mutants affecting the presumed catalytic centre of the selenoenzyme PHGPx were subjected to functional analysis. The rate constants k+1 and k'+2, for the oxidation and the regeneration of the ground state enzyme were estimated, respectively. Moreover, the alkylation rate of the reactive centre by iodoacetate (kinact.) was also analysed. The substitution of the catalytically competent selenocysteine 46 by cysteine (PHGPxcys46) decreased k+1 and k'+2 by about three orders of magnitude, although leaving unaffected kinact.. Furthermore, mutations of PHGPxcys46 involving the other residues of the triad decreased both kinact. and k+1, thus highlighting the involvement of Gln 81 and Trp 136 in the dissociation/activation of the nucleophilic cysteine thiol. In general, substitutions of Gln 81 or Trp 136 by acidic residues in PHGPxcys46 most dramatically depressed the k+1 values, because they practically prevented the dissociation of the thiol group, while neutral or positively charged residues in these positions allowed an intermediate dissociation and induced a corresponding reactivity of the thiol. Our data, for the first time, reveal that the presumed triad of selenocysteine, glutamine and tryptophan residues represents a novel type of catalytic centre, whose integrity is essential for the full catalytic function of glutathione peroxidases.

biological chemistry hoppe-seyler

Probing the Presumed Catalytic Triad of Selenium-Containing Peroxidases by Mutational Analysis of Phospholipid Hydroperoxide Glutathione Peroxidase (PHGPx)