Linked Life Data

1677270

Source:http://linkedlifedata.com/resource/pubmed/id/1677270

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
30
pubmed:dateCreated
1991-8-27
pubmed:abstractText
The Y70F mutant of aspartate aminotransferase has reduced affinity for coenzymes compared to the wild type. The equilibrium dissociation constants for pyridoxamine phosphate (PMP) holoenzymes, KPMPdiss, were determined from the association and dissociation rate constants to be 1.3 nM and 30 nM for the wild type and mutant, respectively. This increase in KPMPdiss for Y70F is due to a 27-fold increase in the dissociation rate constant. Pyridoxal phosphate (PLP) association kinetics are complex, with three kinetic processes detectable for wild type and two for Y70F. A directly determined, accurate value of KPLPdiss for wild type enzyme has been difficult to obtain because of the low value of this constant. The values of KPLPdiss for the holoenzymes were determined indirectly through the measured values for KPMPdiss, glutamate-alpha-ketoglutarate half-reaction equilibrium constants, and the equilibrium constant for the transamination of PLP by glutamate catalyzed by Y70F. The values of KPLPdiss obtained by this procedure are 0.4 pM for wild type and 40 pM for Y70F. The increases in KPMPdiss and KPLPdiss for Y70F correspond to delta delta G values of 1.9 and 2.7 kcal/mol, respectively, and are directly attributed to the loss of the hydrogen bond from the phenolic hydroxyl group of Tyr70 to the coenzyme phosphate. The delta G for association of PLP with wild type enzyme is 4.7 kcal/mol more favorable than that for PMP.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jul
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
30
pubmed:volume
30
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
7461-6
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1991
pubmed:articleTitle
Kinetics and equilibria for the reactions of coenzymes with wild type and the Y70F mutant of Escherichia coli aspartate aminotransferase.
pubmed:affiliation
Department of Molecular and Cell Biology, University of California, Berkeley 94720.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S.