Linked Life Data

9405050

Source:http://linkedlifedata.com/resource/pubmed/id/9405050

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
51
pubmed:dateCreated
1998-1-22
pubmed:abstractText
The catalytic activity and inhibitor binding energetics of enzymes are often pH-dependent properties. Aspartic proteases comprise an important class of enzyme targets for structure-based drug design. We have performed a complete thermodynamic study of pepstatin binding to plasmepsin II, an aspartic proteinase found in Plasmodium falciparum, using isothermal titration calorimetry and circular dichroism. Thermodynamic parameters (DeltaG, DeltaH, DeltaCp, and DeltaS) were measured as functions of both pH and temperature. In the pH range from 4.5 to 7.0, pepstatin binding is accompanied by proton transfer between the solvent and the complex. We used thermodynamic proton linkage theory to derive both the pH-independent binding energetics for pepstatin and the number and pKa values of ionizable residues whose pKa values change during ligand binding. These residues were identified as the two catalytic aspartates, with pKas of 6.5 and 3.0, and His 164, with a pKa of 7.5, based on the three-dimensional structure of the pepstatin-plasmepsin II complex. At pH 5.0, where the protease has optimum activity, the proton transfer process contributes almost 40% of the total binding free energy change and the total charge of the active-site aspartic acid residues is -1. These experimental results provide direct measurement for the protonation states of the catalytic aspartates in the presence of bound ligands. Comparison of the thermodynamic and structural data for pepstatin binding with human cathepsin D, a lysosomal aspartic protease that shares 35% sequence identity with plasmepsin II, suggests that the energetic differences between these two proteins are due to a higher interdomain flexibility in plasmepsin II.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Dec
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
23
pubmed:volume
36
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
16166-72
pubmed:dateRevised
2009-11-19
pubmed:meshHeading
pubmed:year
1997
pubmed:articleTitle
Dissection of the pH dependence of inhibitor binding energetics for an aspartic protease: direct measurement of the protonation states of the catalytic aspartic acid residues.
pubmed:affiliation
Structural Biochemistry Program, SAIC Frederick, National Cancer Institute-Frederick Cancer Research and Development Center, Frederick, Maryland 21702-1201, USA. xie@ncifcrf.gov
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S.