PDBsum entry 2dqx

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protein links
Hydrolase PDB id
Protein chain
491 a.a. *
Waters ×327
* Residue conservation analysis
PDB id:
Name: Hydrolase
Title: Mutant beta-amylase (w55r) from soy bean
Structure: Beta-amylase. Chain: a. Engineered: yes. Mutation: yes
Source: Glycine max. Soybean. Organism_taxid: 3847. Expressed in: escherichia coli. Expression_system_taxid: 562.
2.20Å     R-factor:   0.206     R-free:   0.252
Authors: K.Ishikawa
Key ref:
K.Ishikawa et al. (2007). Kinetic and structural analysis of enzyme sliding on a substrate: multiple attack in beta-amylase. Biochemistry, 46, 792-798. PubMed id: 17223700 DOI: 10.1021/bi061605w
01-Jun-06     Release date:   08-May-07    
Go to PROCHECK summary

Protein chain
Pfam   ArchSchema ?
Q42795  (Q42795_SOYBN) -  Beta-amylase
496 a.a.
491 a.a.*
Key:    PfamA domain  Secondary structure  CATH domain
* PDB and UniProt seqs differ at 1 residue position (black cross)

 Enzyme reactions 
   Enzyme class: E.C.  - Beta-amylase.
[IntEnz]   [ExPASy]   [KEGG]   [BRENDA]
      Reaction: Hydrolysis of 1,4-alpha-glucosidic linkages in polysaccharides so as to remove successive maltose units from the non-reducing ends of the chains.
 Gene Ontology (GO) functional annotation 
  GO annot!
  Biological process     metabolic process   3 terms 
  Biochemical function     hydrolase activity     3 terms  


DOI no: 10.1021/bi061605w Biochemistry 46:792-798 (2007)
PubMed id: 17223700  
Kinetic and structural analysis of enzyme sliding on a substrate: multiple attack in beta-amylase.
K.Ishikawa, H.Nakatani, Y.Katsuya, C.Fukazawa.
Beta-amylase (EC is starch-hydrolyzing exo-type enzyme that can catalyze the successive liberation of beta-maltose from the nonreducing ends of alpha-1,4-linked glucopyranosyl polymers. There is a well-known phenomenon called multiple or repetitive attack where the enzyme releases several maltose molecules in a single enzyme-substrate complex. In order to understand it further, we examined the beta-amylase-catalyzed reaction using maltooligosaccharides. The Monte Carlo method was applied for simulation of the beta-amylase-catalyzed reaction including the multiple attack mechanism. Through site-directed mutagenesis, we have successfully prepared a mutant enzyme which may be simulated as a multiple attack action reduced one with retaining significant hydrolytic activity. From the results of X-ray structure analysis of the mutant enzyme, it was clarified that one carboxyl residue plays a very important role in the multiple attack. The multiple attack action needs the force of enzyme sliding on the substrate. In addition, it is important for the multiple attack that the enzyme and substrate have the characteristics of a stable productive substrate-enzyme complex through a hydrogen bond between the nonreducing end of the substrate and the carboxyl residue of the enzyme.