Structural insight into the bifunctional mechanism of the glycogen-debranching enzyme TreX from the archaeon Sulfolobus solfataricus.

ABSTRACT: TreX is an archaeal glycogen-debranching enzyme that exists in two oligomeric states in solution, as a dimer and tetramer. Unlike its homologs, TreX from Sulfolobus solfataricus shows dual activities for alpha-1,4-transferase and alpha-1,6-glucosidase. To understand this bifunctional mechanism, we determined the crystal structure of TreX in complex with an acarbose ligand. The acarbose intermediate was covalently bound to Asp363, occupying subsites -1 to -3. Although generally similar to the monomeric structure of isoamylase, TreX exhibits two different active-site configurations depending on its oligomeric state. The N terminus of one subunit is located at the active site of the other molecule, resulting in a reshaping of the active site in the tetramer. This is accompanied by a large shi

SUBMITTER: Woo EJ 

PROVIDER: S-EPMC2661413 | biostudies-literature | 2008 Oct

REPOSITORIES: biostudies-literature