Linked Life Data

16159290

Source:http://linkedlifedata.com/resource/pubmed/id/16159290

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
37
pubmed:dateCreated
2005-9-14
pubmed:abstractText
The important biosynthetic intermediate chorismate reacts thermally by two competitive pathways, one leading to 4-hydroxybenzoate via elimination of the enolpyruvyl side chain, and the other to prephenate by a facile Claisen rearrangement. Measurements with isotopically labeled chorismate derivatives indicate that both are concerted sigmatropic processes, controlled by the orientation of the enolpyruvyl group. In the elimination reaction of [4-2H]chorismate, roughly 60% of the label was found in pyruvate after 3 h at 60 degrees C. Moreover, a 1.846 +/- 0.057 2H isotope effect for the transferred hydrogen atom and a 1.0374 +/- 0.0005 18O isotope effect for the ether oxygen show that the transition state for this process is highly asymmetric, with hydrogen atom transfer from C4 to C9 significantly less advanced than C-O bond cleavage. In the competing Claisen rearrangement, a very large 18O isotope effect at the bond-breaking position (1.0482 +/- 0.0005) and a smaller 13C isotope effect at the bond-making position (1.0118 +/- 0.0004) were determined. Isotope effects of similar magnitude characterized the transformations catalyzed by evolutionarily unrelated chorismate mutases from Escherichia coli and Bacillus subtilis. The enzymatic reactions, like their solution counterpart, are thus concerted [3,3]-sigmatropic processes in which C-C bond formation lags behind C-O bond cleavage. However, as substantially larger 18O and smaller 13C isotope effects were observed for a mutant enzyme in which chemistry is fully rate determining, the ionic active site may favor a somewhat more polarized transition state than that seen in solution.
pubmed:grant
pubmed:commentsCorrections
http://linkedlifedata.com/resource/pubmed/commentcorrection/16159290-10103029, http://linkedlifedata.com/resource/pubmed/commentcorrection/16159290-11937513, http://linkedlifedata.com/resource/pubmed/commentcorrection/16159290-12630863, http://linkedlifedata.com/resource/pubmed/commentcorrection/16159290-4731190, http://linkedlifedata.com/resource/pubmed/commentcorrection/16159290-6354259, http://linkedlifedata.com/resource/pubmed/commentcorrection/16159290-6768960, http://linkedlifedata.com/resource/pubmed/commentcorrection/16159290-7500944, http://linkedlifedata.com/resource/pubmed/commentcorrection/16159290-8046752, http://linkedlifedata.com/resource/pubmed/commentcorrection/16159290-8378335, http://linkedlifedata.com/resource/pubmed/commentcorrection/16159290-8660575, http://linkedlifedata.com/resource/pubmed/commentcorrection/16159290-8982005, http://linkedlifedata.com/resource/pubmed/commentcorrection/16159290-9383421, http://linkedlifedata.com/resource/pubmed/commentcorrection/16159290-9665711
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Sep
pubmed:issn
0002-7863
pubmed:author
pubmed:issnType
Print
pubmed:day
21
pubmed:volume
127
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
12957-64
pubmed:dateRevised
2010-10-4
pubmed:meshHeading
pubmed:year
2005
pubmed:articleTitle
Isotope effects on the enzymatic and nonenzymatic reactions of chorismate.
pubmed:affiliation
Institute for Enzyme Research and Department of Biochemistry, University of Wisconsin, 1710 University Avenue, Madison, Wisconsin 53726, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, U.S. Gov't, Non-P.H.S., Research Support, Non-U.S. Gov't, Research Support, N.I.H., Extramural