Linked Life Data

1417785

Source:http://linkedlifedata.com/resource/pubmed/id/1417785

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:dateCreated
1992-11-10
pubmed:abstractText
I.r. spectroscopy has been applied to the study of hydrogen-bonding of the unique ester carbonyl group of acylchymotrypsins in the oxyanion hole of the enzyme. This catalytic device provides electrophilic stabilization of negative charge in the transition states and tetrahedral intermediates along the reaction pathway. The use of 13C isotope substitution of the ester carbonyl group reinforces the previous observation [White & Wharton (1990) Biochem. J. 270, 627-637] that the ester carbonyl group is significantly polarized in the ground state by hydrogen bonding in the oxyanion hole. I.r. difference spectra of [carbonyl-12C]-minus [carbonyl-13C]-cinnamoyl-chymotrypsin as well as each of these acylenzymes minus free enzyme are reported. These spectra show that the contribution of protein perturbation (i.e. spectral features that arise from the enzyme which is distorted on acylation) in [carbonyl-12C]cinnamoyl-chymotrypsin minus free enzyme spectra is significant. The contribution of the perturbation components of the spectra is pH-dependent and can represent up to 50% of the total absorbance in the spectral region from 1690 to 1740 cm-1. Use of the isotopic difference method has allowed problems associated with protein perturbation to be eliminated. Similar difference spectra are presented for dihydrocinnamoyl-chymotrypsin. In this case the effect of perturbation is very marked and leads to the cancellation of the band assigned to the non-bonded conformation of the acyl group which has previously only been observed at higher pH. The isotopic difference method again proves reliable and shows that the frequency difference previously used to calculate the ground-state electronic strain induced by the oxyanion-hole catalytic device is not affected by the perturbation, although the amplitudes of the spectral features are different. A study of the deacylation of cinnamoyl-chymotrypsin in water and deuterium oxide using both u.v. and i.r. spectroscopies has confirmed that the use of deuterium oxide as solvent has no serious effect on the deacylation behaviour of the enzyme. I.r. bands assigned to nonproductive and productive conformers decline identically during deacylation, which shows that the conformers are in dynamic exchange on the reaction time-scale.
pubmed:commentsCorrections
http://linkedlifedata.com/resource/pubmed/commentcorrection/1417785-1889550, http://linkedlifedata.com/resource/pubmed/commentcorrection/1417785-2029519, http://linkedlifedata.com/resource/pubmed/commentcorrection/1417785-2241898, http://linkedlifedata.com/resource/pubmed/commentcorrection/1417785-2271679, http://linkedlifedata.com/resource/pubmed/commentcorrection/1417785-2539813, http://linkedlifedata.com/resource/pubmed/commentcorrection/1417785-2543979, http://linkedlifedata.com/resource/pubmed/commentcorrection/1417785-2790025, http://linkedlifedata.com/resource/pubmed/commentcorrection/1417785-3513759, http://linkedlifedata.com/resource/pubmed/commentcorrection/1417785-3607038, http://linkedlifedata.com/resource/pubmed/commentcorrection/1417785-4689953, http://linkedlifedata.com/resource/pubmed/commentcorrection/1417785-4819756, http://linkedlifedata.com/resource/pubmed/commentcorrection/1417785-5494034, http://linkedlifedata.com/resource/pubmed/commentcorrection/1417785-7356939
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Oct
pubmed:issn
0264-6021
pubmed:author
pubmed:issnType
Print
pubmed:day
1
pubmed:volume
287 ( Pt 1)
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
317-23
pubmed:dateRevised
2010-9-7
pubmed:meshHeading
pubmed:year
1992
pubmed:articleTitle
Analysis and elimination of protein perturbation in infrared difference spectra of acyl-chymotrypsin ester carbonyl groups by using 13C isotopic substitution.
pubmed:affiliation
School of Biochemistry, University of Birmingham, Edgbaston, U.K.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't