Linked Life Data

16244360

Source:http://linkedlifedata.com/resource/pubmed/id/16244360

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
51
pubmed:dateCreated
2005-12-19
pubmed:abstractText
Catalase-peroxidases (KatG) are bifunctional heme peroxidases with an overwhelming catalatic activity. The structures show that the buried heme b is connected to the exterior of the enzyme by a main channel built up by KatG-specific loops named large loop LL1 and LL2, the former containing the highly conserved sequence Met-Gly-Leu-Ile-Tyr-Val-Asn-Pro-Glu-Gly. LL1 residues Ile248, Asn251, Pro252, and Glu253 of KatG from Synechocystis are the focus of this study because of their exposure to the solute matrix of the access channel. In particular, the I248F, N251L, P252A, E253Q, and E253D mutants have been analyzed by UV-visible and resonance Raman spectroscopies in combination with steady-state and presteady-state kinetic analyses. Exchange of these residues did not alter the kinetics of cyanide binding or the overall peroxidase activity. Moreover, the kinetics of compound I formation and reduction by one-electron donors was similar in the variants and the wild-type enzyme. However, the turnover numbers of the catalase activity of I248F, N251L, E253Q, and E253D were only 12.3, 32.6, 25, and 42% of the wild-type activity, respectively. These findings demonstrate that the oxidation reaction of hydrogen peroxide (not its reduction) was affected by these mutations. The altered kinetics allowed us to monitor the spectral features of the dominating redox intermediate of E253Q in the catalase cycle. Resonance Raman data and structural analysis demonstrated the existence of a very rigid and ordered structure built up by the interactions of these residues with distal side and also (via LL1) proximal side amino acids, with the heme itself, and with the solute matrix in the channel. The role of Glu253 and the other investigated channel residues in maintaining an ordered matrix of oriented water dipoles, which guides hydrogen peroxide to its site of oxidation, is discussed.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Dec
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
23
pubmed:volume
280
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
42411-22
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
2005
pubmed:articleTitle
Role of the main access channel of catalase-peroxidase in catalysis.
pubmed:affiliation
Department of Chemistry, Division of Biochemistry, BOKU-University of Natural Resources and Applied Life Sciences, Muthgasse 18, A-1190 Vienna, Austria.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't