2A2C

x-ray structure of human N-acetyl galactosamine kinase complexed with Mg-ADP and N-acetyl galactosamine 1-phosphate

Summary for 2A2C

• Entry DOI: 10.2210/pdb2a2c/pdb
• Related: 2A2C
• Descriptor: N-acetylgalactosamine kinase, 2-acetamido-2-deoxy-1-O-phosphono-alpha-D-galactopyranose, MAGNESIUM ION, ... (7 entities in total)
• Functional Keywords: kinase, galactokinase, transferase
• Biological source: Homo sapiens
• Total number of polymer chains: 1
• Total formula weight: 53599.78

Authors

Thoden, J.B.,Holden, H.M. (deposition date: 2005-06-22, release date: 2005-07-26, Last modification date: 2024-02-14)

Primary citation

Thoden, J.B.,Holden, H.M.
The molecular architecture of human N-acetylgalactosamine kinase.
J.Biol.Chem., 280:32784-32791, 2005

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.

PubMed: 16006554
DOI: 10.1074/jbc.M505730200

Experimental method

X-RAY DIFFRACTION (1.65 Å)