1CPU

SUBSITE MAPPING OF THE ACTIVE SITE OF HUMAN PANCREATIC ALPHA-AMYLASE USING SUBSTRATES, THE PHARMACOLOGICAL INHIBITOR ACARBOSE, AND AN ACTIVE SITE VARIANT


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.00 Å
  • R-Value Work: 0.170 
  • R-Value Observed: 0.170 

wwPDB Validation   3D Report Full Report


This is version 3.2 of the entry. See complete history


Literature

Subsite mapping of the human pancreatic alpha-amylase active site through structural, kinetic, and mutagenesis techniques.

Brayer, G.D.Sidhu, G.Maurus, R.Rydberg, E.H.Braun, C.Wang, Y.Nguyen, N.T.Overall, C.M.Withers, S.G.

(2000) Biochemistry 39: 4778-4791

  • DOI: https://doi.org/10.1021/bi9921182
  • Primary Citation of Related Structures:  
    1CPU, 2CPU, 3CPU

  • PubMed Abstract: 

    We report a multifaceted study of the active site region of human pancreatic alpha-amylase. Through a series of novel kinetic analyses using malto-oligosaccharides and malto-oligosaccharyl fluorides, an overall cleavage action pattern for this enzyme has been developed. The preferred binding/cleavage mode occurs when a maltose residue serves as the leaving group (aglycone sites +1 and +2) and there are three sugars in the glycon (-1, -2, -3) sites. Overall it appears that five binding subsites span the active site, although an additional glycon subsite appears to be a significant factor in the binding of longer substrates. Kinetic parameters for the cleavage of substrates modified at the 2 and 4' ' positions also highlight the importance of these hydroxyl groups for catalysis and identify the rate-determining step. Further kinetic and structural studies pinpoint Asp197 as being the likely nucleophile in catalysis, with substitution of this residue leading to an approximately 10(6)-fold drop in catalytic activity. Structural studies show that the original pseudo-tetrasaccharide structure of acarbose is modified upon binding, presumably through a series of hydrolysis and transglycosylation reactions. The end result is a pseudo-pentasaccharide moiety that spans the active site region with its N-linked "glycosidic" bond positioned at the normal site of cleavage. Interestingly, the side chains of Glu233 and Asp300, along with a water molecule, are aligned about the inhibitor N-linked glycosidic bond in a manner suggesting that these might act individually or collectively in the role of acid/base catalyst in the reaction mechanism. Indeed, kinetic analyses show that substitution of the side chains of either Glu233 or Asp300 leads to as much as a approximately 10(3)-fold decrease in catalytic activity. Structural analyses of the Asp300Asn variant of human pancreatic alpha-amylase and its complex with acarbose clearly demonstrate the importance of Asp300 to the mode of inhibitor binding.


  • Organizational Affiliation

    Department of Biochemistry, University of British Columbia, Vancouver V6T 1Z3, Canada. brayer@laue.biochem.ubc.ca


Macromolecules
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
PROTEIN (ALPHA-AMYLASE)496Homo sapiensMutation(s): 0 
EC: 3.2.1.1
UniProt & NIH Common Fund Data Resources
Find proteins for P04746 (Homo sapiens)
Explore P04746 
Go to UniProtKB:  P04746
PHAROS:  P04746
GTEx:  ENSG00000243480 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP04746
Glycosylation
Glycosylation Sites: 1Go to GlyGen: P04746-1
Sequence Annotations
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  • Reference Sequence
Oligosaccharides

Help

Entity ID: 2
MoleculeChains Length2D Diagram Glycosylation3D Interactions
4-amino-4,6-dideoxy-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose
B
2N/A
Glycosylation Resources
GlyTouCan:  G90989WB
GlyCosmos:  G90989WB
Entity ID: 3
MoleculeChains Length2D Diagram Glycosylation3D Interactions
alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose
C
2N/A
Glycosylation Resources
GlyTouCan:  G07411ON
GlyCosmos:  G07411ON
Small Molecules
Modified Residues  1 Unique
IDChains TypeFormula2D DiagramParent
PCA
Query on PCA
A
L-PEPTIDE LINKINGC5 H7 N O3GLN
Biologically Interesting Molecules (External Reference) 1 Unique
Entity ID: 3
IDChains NameType/Class2D Diagram3D Interactions
PRD_900001
Query on PRD_900001
C
alpha-maltoseOligosaccharide / Nutrient
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.00 Å
  • R-Value Work: 0.170 
  • R-Value Observed: 0.170 
  • Space Group: P 21 21 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 52.91α = 90
b = 68.9β = 90
c = 131.77γ = 90
Software Package:
Software NamePurpose
X-PLORrefinement

Structure Validation

View Full Validation Report



Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 1999-06-14
    Type: Initial release
  • Version 1.1: 2008-04-26
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Non-polymer description, Version format compliance
  • Version 2.0: 2019-12-25
    Changes: Data collection, Database references, Derived calculations, Polymer sequence
  • Version 3.0: 2020-07-29
    Type: Remediation
    Reason: Carbohydrate remediation
    Changes: Atomic model, Data collection, Derived calculations, Structure summary
  • Version 3.1: 2023-12-27
    Changes: Data collection, Database references, Derived calculations, Structure summary
  • Version 3.2: 2024-10-30
    Changes: Structure summary