Linked Life Data

8962674

Source:http://linkedlifedata.com/resource/pubmed/id/8962674

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
11
pubmed:dateCreated
1996-12-4
pubmed:abstractText
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.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Nov
pubmed:issn
0177-3593
pubmed:author
pubmed:issnType
Print
pubmed:volume
376
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
651-60
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1995
pubmed:articleTitle
Probing the presumed catalytic triad of selenium-containing peroxidases by mutational analysis of phospholipid hydroperoxide glutathione peroxidase (PHGPx).
pubmed:affiliation
Department of Biological Chemistry, University of Padova, Italy.
pubmed:publicationType
Journal Article