Linked Life Data

10620336

Source:http://linkedlifedata.com/resource/pubmed/id/10620336

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
1
pubmed:dateCreated
2000-2-9
pubmed:abstractText
Transient and steady state kinetics, together with a range of chromatographic and spectroscopic techniques, have been used to establish the mechanism and the products of the H(2)O(2)-dependent oxidation of p-cresol by ascorbate peroxidase (APX). HPLC, GC-MS, and NMR analyses are consistent with the formation of 2, 2'-dihydroxy-5,5'-dimethylbiphenyl (II) and 4alpha,9beta-dihydro-8, 9beta-dimethyl-3(4H)-dibenzofuranone (Pummerer's ketone, III) as the major products of the reaction. In the presence of cumene hydroperoxide, two additional products were observed which, from GC and MS analyses, were shown to be 1,1-dimethylbenzylalcohol (IV) and bis-(1-methyl-1-phenyl-ethyl)-peroxide (V). The product ratio II:III was dependent on enzyme concentration: at low concentrations Pummerer's ketone (III) predominates and at high concentrations formation of the biphenyl compound (II) is favored. Steady-state data showed a sigmoidal dependence on [p-cresol] that was consistent with the presence of 2.01 +/- 0.15 binding sites for the substrate (25.0 degrees C, sodium phosphate, pH 7.0, mu = 2.2 mM) and independent of ionic strength in the range 2.2-500 mM. Single turnover kinetic experiments (pH 7.0, 5.0 degrees C, mu = 0.10 M) yielded second-order rate constants for Compound I reduction by p-cresol, k(2), of 5.42 +/- 0.10 x 10(5) M(-1) s(-1), respectively. Rate-limiting reduction of Compound II by p-cresol, k(3), showed saturation kinetics, giving values for K(d) = 1.54 +/- 0.12 x 10(-3) M and k(3) = 18.5 +/- 0.7 s(-1). The results are discussed in the more general context of APX-catalyzed aromatic oxidations.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jan
pubmed:issn
0003-9861
pubmed:author
pubmed:copyrightInfo
Copyright 2000 Academic Press.
pubmed:issnType
Print
pubmed:day
1
pubmed:volume
373
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
175-81
pubmed:dateRevised
2011-11-17
pubmed:meshHeading
pubmed:year
2000
pubmed:articleTitle
Catalytic oxidation of p-cresol by ascorbate peroxidase.
pubmed:affiliation
Department of Chemistry, University of Leicester, University Road, Leicester, LE1 7RH, England.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't