4HOW

The crystal structure of isomaltulose synthase from Erwinia rhapontici NX5

Summary for 4HOW

• Entry DOI: 10.2210/pdb4how/pdb
• Related: 4HOX 4HOZ 4HP5 4HPH
• Descriptor: Sucrose isomerase, GLYCEROL, CALCIUM ION, ... (4 entities in total)
• Functional Keywords: tim barrel, isomerase, hydrolase, calcium binding
• Biological source: Erwinia rhapontici
• Total number of polymer chains: 1
• Total formula weight: 70297.13

Authors

Xu, Z.,Li, S.,Xu, H.,Zhou, J. (deposition date: 2012-10-22, release date: 2013-10-16, Last modification date: 2023-11-08)

Primary citation

Xu, Z.,Li, S.,Li, J.,Li, Y.,Feng, X.,Wang, R.,Xu, H.,Zhou, J.
The Structural Basis of Erwinia rhapontici Isomaltulose Synthase
Plos One, 8:e74788-e74788, 2013

PubMed Abstract: Sucrose isomerase NX-5 from Erwiniarhapontici efficiently catalyzes the isomerization of sucrose to isomaltulose (main product) and trehalulose (by-product). To investigate the molecular mechanism controlling sucrose isomer formation, we determined the crystal structures of native NX-5 and its mutant complexes E295Q/sucrose and D241A/glucose at 1.70 Å, 1.70 Å and 2.00 Å, respectively. The overall structure and active site architecture of NX-5 resemble those of other reported sucrose isomerases. Strikingly, the substrate binding mode of NX-5 is also similar to that of trehalulose synthase from Pseudomonasmesoacidophila MX-45 (MutB). Detailed structural analysis revealed the catalytic RXDRX motif and the adjacent 10-residue loop of NX-5 and isomaltulose synthase PalI from Klebsiella sp. LX3 adopt a distinct orientation from those of trehalulose synthases. Mutations of the loop region of NX-5 resulted in significant changes of the product ratio between isomaltulose and trehalulose. The molecular dynamics simulation data supported the product specificity of NX-5 towards isomaltulose and the role of the loop(330-339) in NX-5 catalysis. This work should prove useful for the engineering of sucrose isomerase for industrial carbohydrate biotransformations.

PubMed: 24069347
DOI: 10.1371/journal.pone.0074788

Experimental method

X-RAY DIFFRACTION (1.7 Å)