Crystal Structure of Soybean Beta-Amylase Complexed with Maltose

Experimental Data Snapshot

  • Resolution: 1.86 Å
  • R-Value Free: 0.213 
  • R-Value Work: 0.174 
  • R-Value Observed: 0.174 

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Structural and Enzymatic Analysis of Soybean {beta}-Amylase Mutants with Increased pH Optimum

Hirata, A.Adachi, M.Sekine, A.Kang, Y.N.Utsumi, S.Mikami, B.

(2004) J Biol Chem 279: 7287-7295

  • DOI: https://doi.org/10.1074/jbc.M309411200
  • Primary Citation of Related Structures:  
    1Q6C, 1Q6D, 1Q6E, 1Q6F, 1Q6G

  • PubMed Abstract: 

    Comparison of the architecture around the active site of soybean beta-amylase and Bacillus cereus beta-amylase showed that the hydrogen bond networks (Glu380-(Lys295-Met51) and Glu380-Asn340-Glu178) in soybean beta-amylase around the base catalytic residue, Glu380, seem to contribute to the lower pH optimum of soybean beta-amylase. To convert the pH optimum of soybean beta-amylase (pH 5.4) to that of the bacterial type enzyme (pH 6.7), three mutants of soybean beta-amylase, M51T, E178Y, and N340T, were constructed such that the hydrogen bond networks were removed by site-directed mutagenesis. The kinetic analysis showed that the pH optimum of all mutants shifted dramatically to a neutral pH (range, from 5.4 to 6.0-6.6). The Km values of the mutants were almost the same as that of soybean beta-amylase except in the case of M51T, while the Vmax values of all mutants were low compared with that of soybean beta-amylase. The crystal structure analysis of the wild type-maltose and mutant-maltose complexes showed that the direct hydrogen bond between Glu380 and Asn340 was completely disrupted in the mutants M51T, E178Y, and N340T. In the case of M51T, the hydrogen bond between Glu380 and Lys295 was also disrupted. These results indicated that the reduced pKa value of Glu380 is stabilized by the hydrogen bond network and is responsible for the lower pH optimum of soybean beta-amylase compared with that of the bacterial beta-amylase.

  • Organizational Affiliation

    Laboratory of Food Quality Design and Development, Graduate School of Agriculture, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
beta-amylase495Glycine maxMutation(s): 0 
Find proteins for P10538 (Glycine max)
Explore P10538 
Go to UniProtKB:  P10538
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP10538
Sequence Annotations
  • Reference Sequence


Entity ID: 2
MoleculeChains Length2D Diagram Glycosylation3D Interactions
B, C
Glycosylation Resources
GlyTouCan:  G07411ON
GlyCosmos:  G07411ON
Small Molecules
Ligands 1 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
Query on SO4

Download Ideal Coordinates CCD File 
O4 S
Biologically Interesting Molecules (External Reference) 1 Unique
Experimental Data & Validation

Experimental Data

  • Resolution: 1.86 Å
  • R-Value Free: 0.213 
  • R-Value Work: 0.174 
  • R-Value Observed: 0.174 
  • Space Group: P 31 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 86.158α = 90
b = 86.158β = 90
c = 144.608γ = 120
Software Package:
Software NamePurpose

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2004-02-24
    Type: Initial release
  • Version 1.1: 2008-04-29
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2017-10-11
    Changes: Refinement description
  • Version 2.0: 2020-07-29
    Type: Remediation
    Reason: Carbohydrate remediation
    Changes: Atomic model, Data collection, Derived calculations, Structure summary
  • Version 2.1: 2024-03-13
    Changes: Data collection, Database references, Structure summary