X-ray structure of human n-acetyl galactosamine kinase complexed with Mn-AMPPNP and n-acetyl glactosamine

Experimental Data Snapshot

  • Resolution: 2.20 Å
  • R-Value Free: 0.247 
  • R-Value Work: 0.203 
  • R-Value Observed: 0.207 

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The molecular architecture of human N-acetylgalactosamine kinase.

Thoden, J.B.Holden, H.M.

(2005) J Biol Chem 280: 32784-32791

  • DOI: https://doi.org/10.1074/jbc.M505730200
  • Primary Citation of Related Structures:  
    2A2C, 2A2D

  • PubMed Abstract: 

    Galactokinase plays a key role in normal galactose metabolism by catalyzing the conversion of alpha-d-galactose to galactose 1-phosphate. Within recent years, the three-dimensional structures of human galactokinase and two bacterial forms of the enzyme have been determined. Originally, the gene encoding galactokinase in humans was mapped to chromosome 17. An additional gene, encoding a protein with sequence similarity to galactokinase, was subsequently mapped to chromosome 15. Recent reports have shown that this second gene (GALK2) encodes an enzyme with greater activity against GalNAc than galactose. This enzyme, GalNAc kinase, has been implicated in a salvage pathway for the reutilization of free GalNAc derived from the degradation of complex carbohydrates. Here we report the first structural analysis of a GalNAc kinase. The structure of the human enzyme was solved in the presence of MnAMPPNP and GalNAc or MgATP and GalNAc (which resulted in bound products in the active site). The enzyme displays a distinctly bilobal appearance with its active site wedged between the two domains. The N-terminal region is dominated by a seven-stranded mixed beta-sheet, whereas the C-terminal motif contains two layers of anti-parallel beta-sheet. The overall topology displayed by GalNAc kinase places it into the GHMP superfamily of enzymes, which generally function as small molecule kinases. From this investigation, the geometry of the GalNAc kinase active site before and after catalysis has been revealed, and the determinants of substrate specificity have been defined on a molecular level.

  • Organizational Affiliation

    Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, USA.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
N-acetylgalactosamine kinase478Homo sapiensMutation(s): 0 
Gene Names: GALK2GK2
EC: 2.7.1
UniProt & NIH Common Fund Data Resources
Find proteins for Q01415 (Homo sapiens)
Explore Q01415 
Go to UniProtKB:  Q01415
PHAROS:  Q01415
GTEx:  ENSG00000156958 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ01415
Sequence Annotations
  • Reference Sequence
Small Molecules
Ligands 3 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
Query on ANP

Download Ideal Coordinates CCD File 
C10 H17 N6 O12 P3
Query on A2G

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B [auth A]2-acetamido-2-deoxy-alpha-D-galactopyranose
C8 H15 N O6
Query on MN

Download Ideal Coordinates CCD File 
Experimental Data & Validation

Experimental Data

  • Resolution: 2.20 Å
  • R-Value Free: 0.247 
  • R-Value Work: 0.203 
  • R-Value Observed: 0.207 
  • Space Group: P 65
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 119.1α = 90
b = 119.1β = 90
c = 65.9γ = 120
Software Package:
Software NamePurpose
PROTEUM PLUSdata collection
SAINTdata reduction
PROTEUM PLUSdata reduction
SAINTdata scaling

Structure Validation

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Ligand Structure Quality Assessment 

Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2005-07-05
    Type: Initial release
  • Version 1.1: 2008-04-30
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 2.0: 2020-07-29
    Type: Remediation
    Reason: Carbohydrate remediation
    Changes: Atomic model, Data collection, Database references, Derived calculations, Structure summary
  • Version 2.1: 2023-08-23
    Changes: Data collection, Database references, Refinement description, Structure summary