7taa

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spinqualitylabelsall models 7taa, resolution 1.98Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

FAMILY 13 ALPHA AMYLASE IN COMPLEX WITH ACARBOSE

Overview

The three-dimensional structure of the Aspergillus oryzae alpha-amylase, (TAKA-amylase), in complex with the inhibitor acarbose, has been, determined by X-ray crystallography at a resolution of 1. 98 A. The, tetrasaccharide inhibitor is present as a hexasaccharide presumably, resulting from a transglycosylation event. The hexasaccharide occupies the, -3 to +3 subsites of the enzyme, consistent with the known number of, subsites determined by kinetic studies, with the acarbose unit itself in, the -1 to +3 subsites of the enzyme. The transition state mimicking, unsaturated pseudo-saccharide occupies the -1 subsite as expected and is, present in a distorted 2H3 half-chair conformation. Careful refinement, plus extremely well-resolved unbiased electron density suggest that the, hexasaccharide represents a genuine transglycosylation product, but the, possibility that this apparent species results from an overlapping network, of tetrasaccharides is also discussed. Catalysis by alpha-amylase involves, the hydrolysis of the alpha-1,4 linkages in amylose with a net retention, of the anomeric configuration, via a double-displacement mechanism, as, originally outlined by Koshland [Koshland, D. E. (1953) Biol. Rev. 28, 416-336]. The enzymatic acid/base and nucleophile, residues Glu230 and, Asp206, respectively, are appropriately positioned for catalysis in this, complex, and the hexasaccharide species allows mapping of all the, noncovalent interactions between protein and ligand through the enzyme's, six subsites.

About this Structure

7TAA is a Single protein structure of sequence from Aspergillus oryzae with ABC and CA as ligands. Active as Alpha-amylase, with EC number 3.2.1.1 Full crystallographic information is available from OCA.

Reference

Structure of the Aspergillus oryzae alpha-amylase complexed with the inhibitor acarbose at 2.0 A resolution., Brzozowski AM, Davies GJ, Biochemistry. 1997 Sep 9;36(36):10837-45. PMID:9283074

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