Linked Life Data

7493935

Source:http://linkedlifedata.com/resource/pubmed/id/7493935

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
49
pubmed:dateCreated
1996-1-11
pubmed:abstractText
Kinetic as well as chemical modification studies have implicated the presence of an active site arginine in choline acetyltransferase, whose function is to stabilize coenzyme binding by interacting with the 3'-phosphate of the coenzyme A substrate. In order to identify this residue seven conserved arginines in rat choline acetyltransferase were converted to alanine by site-directed mutagenesis, and the properties of these mutants were compared with the wild type enzyme. Substitution of arginine 452 with alanine resulted in a 7-12-fold increase in the Km for both CoA and acetylcholine as well as kcat, with little change in the Km for dephospho-CoA. Product inhibition studies showed choline to be a competitive inhibitor with respect to acetylcholine, indicating R452A follows the same Theorell-Chance kinetic mechanism as the wild type enzyme. Similar results were obtained with R452Q and R452E, with the latter showing the largest changes in kinetic parameters. These findings are consistent with Arg-452 mutations increasing the rate constant, k5, for dissociation of the coenzyme from the enzyme. Direct evidence that arginine 452 is involved in coenzyme A binding was obtained by showing a 5-10-fold decrease in affinity of the R452A mutant for coenzyme A as determined by the ability to protect against phenylglyoxal inactivation as well as thermal inactivation.
pubmed:grant
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
8
pubmed:volume
270
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
29111-6
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1995
pubmed:articleTitle
Identification of an active site arginine in rat choline acetyltransferase by alanine scanning mutagenesis.
pubmed:affiliation
Department of Biochemistry, University of Kentucky, Lexington 40536-0084, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S.