Crystal structure of inactivated Thermotoga maritima invertase in complex with the trisaccharide substrate raffinose

Biochem J. 2006 May 1;395(3):457-62. doi: 10.1042/BJ20051936.


Thermotoga maritima invertase (beta-fructosidase), a member of the glycoside hydrolase family GH-32, readily releases beta-D-fructose from sucrose, raffinose and fructan polymers such as inulin. These carbohydrates represent major carbon and energy sources for prokaryotes and eukaryotes. The invertase cleaves beta-fructopyranosidic linkages by a double-displacement mechanism, which involves a nucleophilic aspartate and a catalytic glutamic acid acting as a general acid/base. The three-dimensional structure of invertase shows a bimodular enzyme with a five bladed beta-propeller catalytic domain linked to a beta-sandwich of unknown function. In the present study we report the crystal structure of the inactivated invertase in interaction with the natural substrate molecule alpha-D-galactopyranosyl-(1,6)-alpha-D-glucopyranosyl-beta-D-fructofuranoside (raffinose) at 1.87 A (1 A=0.1 nm) resolution. The structural analysis of the complex reveals the presence of three binding-subsites, which explains why T. maritima invertase exhibits a higher affinity for raffinose than sucrose, but a lower catalytic efficiency with raffinose as substrate than with sucrose.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aspergillus / enzymology
  • Binding Sites
  • Carbohydrate Conformation
  • Catalytic Domain
  • Cichorium intybus / enzymology
  • Crystallography, X-Ray
  • Enzyme Activation
  • Glycoside Hydrolases / chemistry
  • Glycoside Hydrolases / metabolism
  • Hydrogen Bonding
  • Models, Molecular
  • Protein Binding
  • Protein Structure, Quaternary
  • Raffinose / chemistry*
  • Raffinose / metabolism*
  • Structural Homology, Protein
  • Substrate Specificity
  • Thermotoga maritima / enzymology*
  • Thermotoga maritima / genetics
  • beta-Fructofuranosidase / chemistry*
  • beta-Fructofuranosidase / genetics
  • beta-Fructofuranosidase / metabolism*


  • Glycoside Hydrolases
  • beta-Fructofuranosidase
  • inulinase
  • Raffinose