title: N-acetylgalactosamine kinase: a naturally promiscuous small molecule kinase.
abstract: N-acetylgalactosamine kinase is a member of the GHMP family of small molecule kinases which catalyses the ATP-dependent phosphorylation of N-acetylgalactosamine. It is highly similar in structure and sequence to galactokinase. Alteration of galactokinase at a key tyrosine residue (Tyr-379 in the human enzyme) has been shown to dramatically enhance the substrate range of this enzyme. Here, we investigated the substrate specificity of the wild type N-acetylgalactosamine kinase and demonstrated that it can also catalyse the phosphorylation of N-acetylglucosamine and N-acetylmannosamine. In human N-acetylgalactosamine kinase, the equivalent residue to Tyr-379 in galactokinase is Phe-444. Alteration of this residue did not result in dramatic changes to the specificity of the enzyme. The more relaxed substrate specificity of N-acetylgalactosamine kinase, compared to galactokinase, can be explained by the greater flexibility of a glycine rich loop in the active site of the enzyme. These results suggest that N-acetylgalactosamine kinase is a potential biocatalyst for the phosphorylation of N-acetyl sugars. However, it is unlikely that it will be possible to further broaden the substrate range by alteration of Phe-444.
authors: School of Biological Sciences, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast, UK.
authors: Helena
authors: H
authors: Kristiansson
authors: David J
authors: DJ
authors: Timson
mesh_terms: D000116:Acetylgalactosamine / Q000737:chemistry*; D002241:Carbohydrates / Q000737:chemistry; D002384:Catalysis; D020134:Catalytic Domain; D005686:Galactokinase / Q000737:chemistry; D006595:Hexosamines / Q000737:chemistry*; D006801:Humans; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000737:chemistry*; D013379:Substrate Specificity
chemical_list: D002241:Carbohydrates; D006595:Hexosamines; C101167:N-acetylgalactosamine-1-phosphate kinase; D017853:Phosphotransferases (Alcohol Group Acceptor); D005686:Galactokinase; D000116:Acetylgalactosamine; C002022:N-acetylmannosamine