1oim

File:1oim.jpg

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FAMILY 1 B-GLUCOSIDASE FROM THERMOTOGA MARITIMA

OverviewOverview

The design and synthesis of transition-state mimics reflects the growing, need both to understand enzymatic catalysis and to influence strategies, for therapeutic intervention. Iminosugars are among the most potent, inhibitors of glycosidases. Here, the binding of 1-deoxynojirimycin and, (+)-isofagomine to the "family GH-1" beta-glucosidase of Thermotoga, maritima is investigated by kinetic analysis, isothermal titration, calorimetry, and X-ray crystallography. The binding of both of these, iminosugar inhibitors is driven by a large 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 signatures of these inhibitors are further, highlighted by the markedly different heat capacity values for binding., The pH dependence of catalysis and of inhibition suggests that the, inhibitory species are protonated inhibitors bound to enzymes whose, acid/base and nucleophile are ionized, while calorimetry indicates that, one proton is released from the enzyme upon binding at the pH optimum of, catalysis (pH 5.8). Given that these results contradict earlier proposals, that the binding of racemic isofagomine to sweet almond beta-glucosidase, was entropically driven (Bulow, A. et al. J. Am. Chem. Soc. 2000, 122, 8567-8568), we reinvestigated the binding of 1-deoxynojirimycin and, isofagomine to the sweet almond enzyme. Calorimetry confirms that the, binding of isofagomine to sweet almond beta-glucosidases is, as observed, for the T. maritima enzyme, driven by a large favorable enthalpy. The, crystallographic structures of the native T. maritima beta-glucosidase, and its complexes with isofagomine and 1-deoxynojirimycin, all at, approximately 2.1 A resolution, reveal that additional ordering of bound, solvent may present an entropic penalty to 1-deoxynojirimycin binding that, does not penalize isofagomine.

About this StructureAbout this Structure

1OIM is a Single protein structure of sequence from Thermotoga maritima with as ligand. Active as Beta-glucosidase, with EC number 3.2.1.21 Known structural/functional Site: . Full crystallographic information is available from OCA.

ReferenceReference

Iminosugar glycosidase inhibitors: structural and thermodynamic dissection of the binding of isofagomine and 1-deoxynojirimycin to beta-glucosidases., Zechel DL, Boraston AB, Gloster T, Boraston CM, Macdonald JM, Tilbrook DM, Stick RV, Davies GJ, J Am Chem Soc. 2003 Nov 26;125(47):14313-23. PMID:14624580

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