Linked Life Data

11434770

Source:http://linkedlifedata.com/resource/pubmed/id/11434770

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
27
pubmed:dateCreated
2001-7-3
pubmed:abstractText
Spectroscopic and kinetic methods have been used to explore the roles of divalent metal ions in the enolase-catalyzed dehydration of 2-phosphoglycerate (2-PGA). Enolase requires 2 equiv of metal ion per active site for maximal activity. Previous crystallographic studies [Larsen, T. M., Wedekind, J. E., Rayment, I., and Reed, G. H. (1996) Biochemistry 35, 4349-4358] showed that both magnesium ions coordinated to the carboxylate group of the substrate/product-a scheme consistent with metal ion assistance in formation of the enolate intermediate. Electron paramagnetic resonance (EPR) data with 17O-labeled forms of phosphoenolpyruvate show that Mn(2+), bound at the lower affinity site, coordinates to one carboxylate oxygen and one phosphate oxygen of the substrate. These observations are fully consistent with the crystallographic data. Plots of activity versus log [metal ion] are bell-shaped, and the inhibitory phases of the profiles have been previously attributed to binding of metal ions at ancillary sites on the enzyme. However, the activation profiles and measurements of 2H kinetic isotope effects support an ordered kinetic mechanism wherein binding of 2-PGA precedes binding of the second metal ion, and release of the second metal ion occurs prior to departure of phosphoenolpyruvate. High concentrations of metal ion lead to inhibition in the ordered mechanism by interfering with product release. The 2H kinetic isotope effect is diminished in the inhibitory phases of the metal ion activation profiles in a manner that is consistent with the predominantly ordered mechanism. Zn(2+) gives lower maximal activity than Mg(2+), apparently due to slow release of Zn(2+) from the product complex. Addition of imidazole increases the maximal rate apparently by accelerating the release of Zn(2+) from the enzyme.
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
10
pubmed:volume
40
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
8009-17
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
2001
pubmed:articleTitle
Role of metal ions in catalysis by enolase: an ordered kinetic mechanism for a single substrate enzyme.
pubmed:affiliation
Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53705, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S.