Crystal structure of fructan 1-exohydrolase IIa from Cichorium intybus in complex with sucrose

Experimental Data Snapshot

  • Resolution: 2.50 Å
  • R-Value Free: 0.218 
  • R-Value Work: 0.197 
  • R-Value Observed: 0.197 

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Insights into the fine architecture of the active site of chicory fructan 1-exohydrolase: 1-kestose as substrate vs sucrose as inhibitor.

Verhaest, M.Lammens, W.Le Roy, K.De Ranter, C.J.Van Laere, A.Rabijns, A.Van den Ende, W.

(2007) New Phytol 174: 90-100

  • DOI: https://doi.org/10.1111/j.1469-8137.2007.01988.x
  • Primary Citation of Related Structures:  
    2ADD, 2ADE, 2AEY, 2AEZ

  • PubMed Abstract: 

    * Invertases and fructan exohydrolases (FEHs) fulfil important physiological functions in plants. Sucrose is the typical substrate for invertases and bacterial levansucrases but not for plant FEHs, which are usually inhibited by sucrose. * Here we report on complexes between chicory (Cichorium intybus) 1-FEH IIa with the substrate 1-kestose and the inhibitors sucrose, fructose and 2,5 dideoxy-2,5-imino-D-mannitol. Comparisons with other family GH32 and 68 enzyme-substrate complexes revealed that sucrose can bind as a substrate (invertase/levansucrase) or as an inhibitor (1-FEH IIa). * Sucrose acts as inhibitor because the O2 of the glucose moiety forms an H-linkage with the acid-base catalyst E201, inhibiting catalysis. By contrast, the homologous O3 of the internal fructose in the substrate 1-kestose forms an intramolecular H-linkage and does not interfere with the catalytic process. Mutagenesis showed that W82 and S101 are important for binding sucrose as inhibitor. * The physiological implications of the essential differences in the active sites of FEHs and invertases/levansucrases are discussed. Sucrose-inhibited FEHs show a K(i) (inhibition constant) well below physiological sucrose concentrations and could be rapidly activated under carbon deprivation.

  • Organizational Affiliation

    Laboratorium voor Biokristallografie, Faculteit Farmaceutische Wetenschappen, K.U. Leuven, Herestraat 49, O & N II, bus 822, B-3000 Leuven, Belgium.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
fructan 1-exohydrolase IIa543Cichorium intybusMutation(s): 0 
Gene Names: 1-feh IIa
Find proteins for Q93X60 (Cichorium intybus)
Explore Q93X60 
Go to UniProtKB:  Q93X60
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ93X60
Sequence Annotations
  • Reference Sequence


Entity ID: 2
MoleculeChains Length2D Diagram Glycosylation3D Interactions
Glycosylation Resources
GlyTouCan:  G62182OO
GlyCosmos:  G62182OO
GlyGen:  G62182OO
Entity ID: 3
MoleculeChains Length2D Diagram Glycosylation3D Interactions
Glycosylation Resources
GlyTouCan:  G42666HT
GlyCosmos:  G42666HT
GlyGen:  G42666HT
Entity ID: 4
MoleculeChains Length2D Diagram Glycosylation3D Interactions
Glycosylation Resources
GlyTouCan:  G05551OP
GlyCosmos:  G05551OP
Biologically Interesting Molecules (External Reference) 1 Unique
Experimental Data & Validation

Experimental Data

  • Resolution: 2.50 Å
  • R-Value Free: 0.218 
  • R-Value Work: 0.197 
  • R-Value Observed: 0.197 
  • Space Group: P 41 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 139.32α = 90
b = 139.32β = 90
c = 182.75γ = 90
Software Package:
Software NamePurpose
DENZOdata reduction
SCALEPACKdata scaling

Structure Validation

View Full Validation Report

Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2006-08-29
    Type: Initial release
  • Version 1.1: 2008-04-30
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Non-polymer description, Version format compliance
  • Version 2.0: 2020-07-29
    Type: Remediation
    Reason: Carbohydrate remediation
    Changes: Atomic model, Data collection, Derived calculations, Non-polymer description, Structure summary
  • Version 2.1: 2023-08-23
    Changes: Data collection, Database references, Refinement description, Structure summary