Binding of a possible transition state analogue to the active site of carboxypeptidase A.
The mode of binding of the competitive inhibitor 2-benzyl-3-formylpropanoic acid to the active site of carboxypeptidase A has been studied by x-ray diffraction methods to a resolution of 1.7 A. The actual species bound to the enzyme was determined to be the gem-diol resulting from covalent hydration at the aldehyde carbonyl. Details relating to the process of association of inhibitor with enzyme are unknown at this time: the free aldehyde could initially bind to the enzyme and subsequently undergo catalytic hydration; or, the hydrate itself could be the species initially binding to the enzyme, because it does exist to a high degree (25%) in aqueous solution. Nevertheless, the structure of the complex reported is reminiscent of a possible tetrahedral intermediate that would be encountered in a general base hydrolytic mechanism. Of course, other mechanistic proposals, such as the anhydride pathway, cannot be ruled out simply on the basis of the structure of this enzyme-inhibitor complex.
D001665:Binding Sites; D001667:Binding, Competitive; D002268:Carboxypeptidases / Q000378:metabolism*; D043422:Carboxypeptidases A; D007700:Kinetics; D008958:Models, Molecular; D010666:Phenylpropionates / Q000494:pharmacology; D011485:Protein Binding; D011487:Protein Conformation; D014961:X-Ray Diffraction
D010666:Phenylpropionates; C041630:2-benzyl-3-formylpropanoic acid; D002268:Carboxypeptidases; D043422:Carboxypeptidases A