1KBK

Mechanistic Analyses of Catalysis in Human Pancreatic Alpha-Amylase: Detailed Kinetic and Structural Studies of Mutants of Three Conserved Carboxylic Acids

Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.90 Å
  • R-Value Free: 0.177 
  • R-Value Work: 0.171 

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Literature

Mechanistic analyses of catalysis in human pancreatic alpha-amylase: detailed kinetic and structural studies of mutants of three conserved carboxylic acids.

Rydberg, E.H., Li, C., Maurus, R., Overall, C.M., Brayer, G.D., Withers, S.G.

(2002) Biochemistry 41: 4492-4502

  • DOI: 10.1021/bi011821z
  • Primary Citation of Related Structures:  
    1KBB, 1KBK

  • PubMed Abstract: 

    • The roles of three conserved active site carboxylic acids (D197, E233, and D300) in the catalytic mechanism of human pancreatic alpha-amylase (HPA) were studied by utilizing site-directed mutagenesis in combination with structural and kinetic analyses of the resultant enzymes ...

    The roles of three conserved active site carboxylic acids (D197, E233, and D300) in the catalytic mechanism of human pancreatic alpha-amylase (HPA) were studied by utilizing site-directed mutagenesis in combination with structural and kinetic analyses of the resultant enzymes. All three residues were mutated to both alanine and the respective amide, and a double alanine mutant (E233A/D300A) was also generated. Structural analyses demonstrated that there were no significant differences in global fold for the mutant enzymes. Kinetic analyses were performed on the mutants, utilizing a range of substrates. All results suggested that D197 was the nucleophile, as virtually all activity (>10(5)-fold decrease in k(cat) values) was lost for the enzymes mutated at this position when assayed with several substrates. The significantly greater second-order rate constant of E233 mutants on "activated" substrates (k(cat)/K(m) value for alpha-maltotriosyl fluoride = 15 s(-)(1) mM(-)(1)) compared with "unactivated" substrates (k(cat)/K(m) value for maltopentaose = 0.0030 s(-)(1) mM(-)(1)) strongly suggested that E233 is the general acid catalyst, as did the pH-activity profiles. Transglycosylation was favored over hydrolysis for the reactions of several of the enzymes mutated at D300. At the least, this suggests an overall impairment of the catalytic mechanism where the reaction then proceeds using the better acceptor (oligosaccharide instead of water). This may also suggest that D300 plays a crucial role in enzymic interactions with the nucleophilic water during the hydrolysis of the glycosidic bond.

    Organizational Affiliation: 

    Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada.



Macromolecules
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(by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
ALPHA-AMYLASE, PANCREATICA496Homo sapiensMutation(s): 1 
Gene Names: AMY2A
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
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP04746
Protein Feature View
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  • Reference Sequence
Small Molecules
Ligands 3 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
NAG
Query on NAG
Download Ideal Coordinates CCD File 
B [auth A]2-acetamido-2-deoxy-beta-D-glucopyranose
C8 H15 N O6
OVRNDRQMDRJTHS-FMDGEEDCSA-N		 Ligand Interaction
CA
Query on CA
Download Ideal Coordinates CCD File 
C [auth A]CALCIUM ION
Ca
BHPQYMZQTOCNFJ-UHFFFAOYSA-N		 Ligand Interaction
CL
Query on CL
Download Ideal Coordinates CCD File 
D [auth A]CHLORIDE ION
Cl
VEXZGXHMUGYJMC-UHFFFAOYSA-M		 Ligand Interaction
Modified Residues  1 Unique
IDChainsTypeFormula2D DiagramParent
PCA
Query on PCA		A L-PEPTIDE LINKINGC5 H7 N O3GLN
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.90 Å
  • R-Value Free: 0.177 
  • R-Value Work: 0.171 
  • Space Group: P 21 21 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 52.88α = 90
b = 69.52β = 90
c = 131.6γ = 90
Software Package:
Software NamePurpose
DENZOdata reduction
SCALEPACKdata scaling
CNSrefinement
CNSphasing

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2002-04-10
    Type: Initial release
  • Version 1.1: 2008-04-27
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Non-polymer description, Version format compliance
  • Version 2.0: 2019-12-25
    Changes: Database references, Derived calculations, Polymer sequence
  • Version 2.1: 2020-07-29
    Type: Remediation
    Reason: Carbohydrate remediation
    Changes: Data collection, Derived calculations, Structure summary
  • Version 2.2: 2021-10-27
    Changes: Database references, Structure summary