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Title 

Structural ratio-rials for the short branched substrato soscificity of the glycogen debranching enzyme GlgX

Authors 

Hyung Nam SongTae Yang JungJ T ParkByoung Chul ParkP K MyungW BoosEui-jeon WooK H Park

Publisher 

Wiley-Blackwell

Issue Date 

2010

Citation 

Proteines, vol. 78, no. 8, pp. 1847-1855

Keywords 

GDEGlgXGlycogen catabolismMalto-oligosaccharidesX-ray structure

Abstract 

Glycogen serves as major energy storage in most living organisms. GlgX, with its gene in the glycogen degradation operon, functions in glycogen catabolism by selectively catalyzing the debranching of polysaccharide outer chains in bacterial glycosynthesis. GlgX hydrolyzes α-1,6glycosidic linkages of phosphorylase-limit dextrin containing only three or four glucose subunits produced by glycogen Phosphorylase. To understand its mechanism and unique substrate specificity toward short branched α-polyglucans, we determined the structure of GlgX from Escherichia Coli K12 at 2.25 ? resolution. The structure reveals a monomer consisting of three major domains with high structural similarity to the subunit of TreX, the oligomeric bifunctional glycogen debranching enzyme (GDE) from Sulfolobus. In the overlapping substrate binding groove, conserved residues Leu270, Asp271, and Pro208 block the cleft, yielding a shorter narrow GIgX cleft compared to that of TreX. Residues 207-213 form a unique helical conformation that is observed in both GIgX and TreX, possibly distinguishing GDEs from isoamylases and pullulanases. The structural feature observed at the substrate binding groove provides a molecular explanation for the unique substrate specificity of GlgX for G4 phosphorylase-limit dextrin and the discriminative activity of TreX and GlgX toward substrates of varying lengths.

ISSN 

0887-3585

Link 

http://dx.doi.org/10.1002/prot.22697

Appears in Collections

1. Journal Articles > Journal Articles

Registered Date

2019-05-02


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