1g9h
From Proteopedia
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TERNARY COMPLEX BETWEEN PSYCHROPHILIC ALPHA-AMYLASE, COMII (PSEUDO TRI-SACCHARIDE FROM BAYER) AND TRIS (2-AMINO-2-HYDROXYMETHYL-PROPANE-1,3-DIOL)
Overview
The psychrophilic Pseudoalteromonas haloplanctis alpha-amylase is shown to, form ternary complexes with two alpha-amylase inhibitors present in the, active site region, namely, a molecule of Tris and a trisaccharide, inhibitor or heptasaccharide inhibitor, respectively. The crystal, structures of these complexes have been determined by X-ray, crystallography to 1.80 and 1.74 A resolution, respectively. In both, cases, the prebound inhibitor Tris is expelled from the active site by the, incoming oligosaccharide inhibitor substrate analogue, but stays linked to, it, forming well-defined ternary complexes with the enzyme. These results, illustrate competition in the crystalline state between two inhibitors, an, oligosaccharide substrate analogue and a Tris molecule, bound at the same, time in the active site region. Taken together, these structures show that, the enzyme performs transglycosylation in the complex with the, pseudotetrasaccharide acarbose (confirmed by a mutant structure), leading, to a well-defined heptasaccharide, considered as a more potent inhibitor., Furthermore, the substrate-induced ordering of water molecules within a, channel highlights a possible pathway used for hydrolysis of starch and, related poly- and oligosaccharides.
About this Structure
1G9H is a Single protein structure of sequence from Pseudoalteromonas haloplanktis with CA, CL and TRS as ligands. Active as Alpha-amylase, with EC number 3.2.1.1 Full crystallographic information is available from OCA.
Reference
Crystallographic evidence of a transglycosylation reaction: ternary complexes of a psychrophilic alpha-amylase., Aghajari N, Roth M, Haser R, Biochemistry. 2002 Apr 2;41(13):4273-80. PMID:11914073
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