Linked Life Data

12238925

Source:http://linkedlifedata.com/resource/pubmed/id/12238925

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
20
pubmed:dateCreated
2002-9-19
pubmed:abstractText
Recently, we designed (-)-epicatechin sulfate (ECS), the first small nonsaccharide molecule, as an activator of antithrombin for the accelerated inhibition of factor Xa, a key proteinase of the coagulation cascade (Gunnarsson, G. T.; Desai, U. R. J. Med. Chem. 2002, 45, 1233-1243). Although sulfated flavanoid ECS was found to bind antithrombin with an affinity ( approximately 10.7 microM) comparable to the reference trisaccharide DEF ( approximately 4.5 microM), it accelerated the inhibition of factor Xa only 10-fold as compared to the approximately 300-fold observed with DEF. To determine whether this conformational activation of the inhibitor is dependent on the structure of the organic activator and to probe the basis for the deficiency in activation, we studied the interaction of similar sulfated flavanoids with antithrombin. (+)-Catechin sulfate (CS), a chiral stereoisomer of ECS, bound plasma antithrombin with a 3-fold higher affinity (K(D) = 3.5 microM) and a 2-fold higher second-order rate constant for factor Xa inhibition (k(ACT) = 6750 M(-1) s(-1)). On the contrary, the K(D) and k(ACT) were found to be lower approximately 7.4- and approximately 2.4-fold, respectively, for its racemic counterpart, (+/-)-catechin sulfate. Dependence of the equilibrium dissociation constant on the ionic strength of the medium at pH 6.0 and 7.4 suggests that nonionic interactions contribute a major proportion ( approximately 55-73%) of the total binding energy, and only 1-2 ion pairs, in comparison to the expected approximately 4 ion pairs for the reference trisaccharide, are formed in the interaction. Competitive binding experiments indicate that activator CS does not compete with a saccharide ligand that binds antithrombin in the pentasaccharide binding site, while it competes with full-length low-affinity heparin. A molecular docking study suggests plausible binding of CS in the extended heparin binding site, which is adjacent to the binding domain for the reference trisaccharide DEF. In combination, the results demonstrate that although conformational activation of antithrombin with small sulfated flavanoids is dependent on the structure of the activator, the designed activators do not bind in the pentasaccharide binding site in antithrombin resulting in weak activation. The mechanistic investigation highlights plausible directions to take in the rational design of specific high-affinity organic antithrombin activators.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Sep
pubmed:issn
0022-2623
pubmed:author
pubmed:issnType
Print
pubmed:day
26
pubmed:volume
45
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
4460-70
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
2002
pubmed:articleTitle
Interaction of designed sulfated flavanoids with antithrombin: lessons on the design of organic activators.
pubmed:affiliation
Department of Medicinal Chemistry, Virginia Commonwealth University, 410 North 12th Street, P.O. Box 980540, Richmond, Virginia 23298, USA.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't