Further Evidence for the Critical Role of a Non-Chair Conformation of L-Iduronic Acid in the Activation of Antithrombin
作者:José Kovensky、Jean-Maurice Mallet、Jacques Esnault、Pierre-Alexandre Driguez、Philippe Sizun、Jean-Pascal Hérault、Jean-Marc Herbert、Maurice Petitou、Pierre Sinaÿ
DOI:10.1002/1099-0690(200211)2002:21<3595::aid-ejoc3595>3.0.co;2-f
日期:2002.11
L-iduronic acid, a conformationally flexible monosaccharide, imparts a remarkable protein adaptability to the glycosammoglycans heparin, heparan sulfate, and dermatan sulfate. The pentasaccharide representing the antithrombin binding site of heparin contains one such L-iduronic acid residue, the conformation of which has been suspected for a long time to be a critical factor in the interaction with antithrombin. We have recently synthesized pentasaccharides containing an Liduronic acid residue conformationally forced to exist within a restricted arc (S-2(0) reversible arrow B-2,B-5 reversible arrow S-5(1)) of the overall pseudorotational circle. We could thus demonstrate that the S-2(0) conformation is adopted upon binding to the protein. In the present work, we now describe the synthesis of a similar pentasaccharide containing a slightly more flexible L-iduronic acid unit with a three-atom bridge between C-2 and C5 of the hexopyranose ring. This pentasaccharide is a better activator of AT-III with respect to blood coagulation factor Xa inhibition. These results confirm that L-iduronic acid adopts an unusual non-chair conformation close to S-2(0) and clearly explains how the unique conformational behavior Of L-iduronic acid is the key to heparin's interaction with AT-III.