Linked Life Data

10747802

Source:http://linkedlifedata.com/resource/pubmed/id/10747802

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
14
pubmed:dateCreated
2000-5-2
pubmed:abstractText
The tyrosyl radicals generated in reactions of ethyl hydrogen peroxide with both native and indomethacin-pretreated prostaglandin H synthase 1 (PGHS-1) were examined by low-temperature electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) spectroscopies. In the reaction of peroxide with the native enzyme at 0 degrees C, the tyrosyl radical EPR signal underwent a continuous reduction in line width and lost intensity as the incubation time increased, changing from an initial, 35-G wide doublet to a wide singlet of slightly smaller line width and finally to a 25-G narrow singlet. The 25-G narrow singlet produced by self-inactivation was distinctly broader than the 22-G narrow singlet obtained by indomethacin treatment. Analysis of the narrow singlet EPR spectra of self-inactivated and indomethacin-pretreated enzymes suggests that they reflect conformationally distinct tyrosyl radicals. ENDOR spectroscopy allowed more detailed characterization by providing hyperfine couplings for ring and methylene protons. These results establish that the wide doublet and the 22-G narrow singlet EPR signals arise from tyrosyl radicals with different side-chain conformations. The wide-singlet ENDOR spectrum, however, is best accounted for as a mixture of native wide-doublet and self-inactivated 25-G narrow-singlet species, consistent with an earlier EPR study [DeGray et al. (1992) J. Biol. Chem. 267, 23583-23588]. We conclude that a tyrosyl residue other than the catalytically essential Y385 species is most likely responsible for the indomethacin-inhibited, narrow-singlet spectrum. Thus, this inhibitor may function by redirecting radical formation to a catalytically inactive side chain. Either radical migration or conformational relaxation at Y385 produces the 25-G narrow singlet during self-inactivation. Our ENDOR data also indicate that the catalytically active, wide-doublet species is not hydrogen bonded, which may enhance its reactivity toward the fatty-acid substrate bound nearby.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Apr
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
11
pubmed:volume
39
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
4112-21
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
2000
pubmed:articleTitle
Electron paramagnetic resonance and electron nuclear double resonance spectroscopic identification and characterization of the tyrosyl radicals in prostaglandin H synthase 1.
pubmed:affiliation
Department of Internal Medicine, University of Texas Health Science Center at Houston, Houston, Texas 77225, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S.