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Báo cáo khoa học: Structure of the complex of a yeast glucoamylase with acarbose reveals the presence of a raw starch binding site on the catalytic domain

Most glucoamylases (a-1,4-d-glucan glucohydrolase, EC 3.2.1.3) have structures consisting of both a catalytic and a starch binding domain. The structure of a glucoamylase from Saccharomycopsis fibuligeraHUT 7212 (Glu), determined a few years ago, consists of a single catalytic domain. The structure of this enzyme with the resolution extended to 1.1 A˚ and that of the enzyme–acarbose complex at 1.6 A˚ resolution are presented here. | ềFEBS Journal Structure of the complex of a yeast glucoamylase with acarbose reveals the presence of a raw starch binding site on the catalytic domain Jozef Sevcik1 Eva Hostinova1 Adriana Solovicova1 Juraj Gasperik1 Zbigniew Dauter2 and Keith S. Wilson3 1 Institute of Molecular Biology Slovak Academy of Sciences Bratislava Slovakia 2 Synchrotron Radiation Research Section Macromolecular Crystallography Laboratory NCI Argonne IL USA 3 York StructuralBiology Laboratory University of York UK Keywords acarbose glucoamylase starch binding site sugar tongs X-ray structure Correspondence J. Sevcik Institute of Molecular Biology Slovak Academy of Sciences Dubravska cesta 21 84551 Bratislava Slovakia Fax 421 259307416 Tel 421 259307435 E-mail jozef.sevcik@savba.sk Received 16 January 2006 revised 10 March 2006 accepted 15 March 2006 doi 10.1111 j.1742-4658.2006.05230.x Most glucoamylases a-1 4-D-glucan glucohydrolase EC 3.2.1.3 have structures consisting of both a catalytic and a starch binding domain. The structure of a glucoamylase from Saccharomycopsis fibuligera HUT 7212 Glu determined a few years ago consists of a single catalytic domain. The structure of this enzyme with the resolution extended to 1.1 A and that of the enzyme-acarbose complex at 1.6 A resolution are presented here. The structure at atomic resolution besides its high accuracy shows clearly the influence of cryo-cooling which is manifested in shrinkage of the molecule and lowering the volume of the unit cell. In the structure of the complex two acarbose molecules are bound one at the active site and the second at a site remote from the active site curved around Tyr464 which resembles the inhibitor molecule in the sugar tongs surface binding site in the structure of barley a-amylase isozyme 1 complexed with a thiomaltooligosaccharide. Based on the close similarity in sequence of glucoamylase Glu which does not degrade raw starch to that of glucoamylase Glm from S. fibuligera IFO 0111 a raw .