Iminosugar Glycosidase Inhibitors: Structural and Thermodynamic Dissection of the Binding of Isofagomine and 1-Deoxynojirimycin to mg src="http://pubs.acs.org/images/gifchars/beta2.gif" border="0" a

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• 作者：David L. Zechel ; Alisdair B. Boraston ; Tracey Gloster ; Catherine M. Boraston ; James M. Macdonald ; D. Matthew G. Tilbrook ; Robert V. Stick ; and Gideon J. Davies
• 刊名：Journal of the American Chemical Society
• 出版年：2003
• 出版时间：November 26, 2003
• 年：2003
• 卷：125
• 期：47
• 页码：14313 - 14323
• 全文大小：477K
• 年卷期：v.125,no.47(November 26, 2003)
• ISSN：1520-5126

文摘

The design and synthesis of transition-state mimics reflects the growing need both to understandenzymatic catalysis and to influence strategies for therapeutic intervention. Iminosugars are among themost potent inhibitors of glycosidases. Here, the binding of 1-deoxynojirimycin and (+)-isofagomine to the"family GH-1" mages/gifchars/beta2.gif" BORDER=0 ALIGN="middle">-glucosidase of Thermotoga maritima is investigated by kinetic analysis, isothermal titrationcalorimetry, and X-ray crystallography. The binding of both of these iminosugar inhibitors is driven by alarge and favorable enthalpy. The greater inhibitory power of isofagomine, relative to 1-deoxynojirimycin,however, resides in its significantly more favorable entropy; indeed the differing thermodynamic signaturesof these inhibitors are further highlighted by the markedly different heat capacity values for binding. ThepH dependence of catalysis and of inhibition suggests that the inhibitory species are protonated inhibitorsbound to enzymes whose acid/base and nucleophile are ionized, while calorimetry indicates that one protonis released from the enzyme upon binding at the pH optimum of catalysis (pH 5.8). Given that these resultscontradict earlier proposals that the binding of racemic isofagomine to sweet almond mages/gifchars/beta2.gif" BORDER=0 ALIGN="middle">-glucosidase wasentropically driven (Bülow, A. et al. J. Am. Chem. Soc. 2000, 122, 8567-8568), we reinvestigated thebinding of 1-deoxynojirimycin and isofagomine to the sweet almond enzyme. Calorimetry confirms that thebinding of isofagomine to sweet almond mages/gifchars/beta2.gif" BORDER=0 ALIGN="middle">-glucosidases is, as observed for the T. maritima enzyme, drivenby a large favorable enthalpy. The crystallographic structures of the native T. maritima mages/gifchars/beta2.gif" BORDER=0 ALIGN="middle">-glucosidase, andits complexes with isofagomine and 1-deoxynojirimycin, all at ~2.1 Å resolution, reveal that additionalordering of bound solvent may present an entropic penalty to 1-deoxynojirimycin binding that does notpenalize isofagomine.