Direct measurement of local and global contributions in the binding of coformycin to bovine adenosine deaminase.
A general method is outlined that determines quantitatively the extent to which tight ligand binding to an enzyme active site is facilitated by the adoption of a stabler macromolecular conformation in the complex. The method therefore rejects the general assumption that competitive inhibitor binding to enzyme active sites involves only local (active site) interactions. The procedure involves comparing the unfolding transition state free energies of the free and complexed enzyme from physiological conditions. For the interaction of the transition state analog coformycin with bovine adenosine deaminase we observed that the binding free energy by the physiological enzyme was approximately 92% due to the assumption of a stabler enzyme conformation in the complex. The significance of these findings in terms of general enzyme catalysis is discussed.
Strohmeyer
Esther A
EA
Department of Chemistry and Biochemistry and the Center for Drug Discovery, Baylor University, Waco, TX 76798, USA.
Beckley
Janel R
JR
Britt
B Mark
BM
D000243:Adenosine Deaminase / Q000737:chemistry* / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D002417:Cattle; D003070:Coformycin / Q000493:pharmacokinetics*; D004791:Enzyme Inhibitors / Q000493:pharmacokinetics*; D019791:Guanidine; D007700:Kinetics; D011489:Protein Denaturation / Q000187:drug effects; D013154:Spleen / Q000201:enzymology; D013816:Thermodynamics
D004791:Enzyme Inhibitors; D003070:Coformycin; D000243:Adenosine Deaminase; D019791:Guanidine