Structure of Glucoamylase from Saccharomycopsis fibuligera at 1.7 Å Resolution
Acta Crystallographica Section D
Volume 54, Issue 5, pages 854–866, September 1998
How to Cite
Ševčík, J., Solovicová, A., Hostinová, E., Gašperík, J., Wilson, K. S. and Dauter, Z. (1998), Structure of Glucoamylase from Saccharomycopsis fibuligera at 1.7 Å Resolution. Acta Crystallographica D, 54: 854–866. doi: 10.1107/S0907444998002005
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The yeast Saccharomycopsis fibuligera produces a glucoamylase which belongs to sequence family 15 of glycosyl hydrolases. The structure of the non-glycosylated recombinant enzyme has been determined by molecular replacement and refined against 1.7 Å resolution synchrotron data to an R factor of 14.6%. This is the first report of the three-dimensional structure of a yeast family 15 glucoamylase. The refinement from the initial molecular-replacement model was not straightforward. It involved the use of an unrestrained automated refinement procedure (uARP) in combination with the maximum-likelihood refinement program REFMAC. The enzyme consists of 492 amino-acid residues and has 14 α-helices, 12 of which form an (α/α)6 barrel. It contains a single catalytic domain but no starch-binding domain. The fold of the molecule and the active site are compared to the known structure of the catalytic domain of a fungal family 15 glucoamylase and are shown to be closely similar. The active- and specificity-site residues are especially highly conserved. The model of the acarbose inhibitor from the analysis of the fungal enzyme fits tightly into the present structure. The active-site topology is a pocket and hydrolysis proceeds with inversion of the configuration at the anomeric carbon. The enzyme acts as an exo-glycosyl hydrolase. There is a Tris [2-amino-2-(hydroxymethyl)-1,3-propanediol] molecule acting as an inhibitor in the active-site pocket.