title: Insights into the binding specificity and catalytic mechanism of N-acetylhexosamine 1-phosphate kinases through multiple reaction complexes.
abstract: Utilization of N-acetylhexosamine in bifidobacteria requires the specific lacto-N-biose/galacto-N-biose pathway, a pathway differing from the Leloir pathway while establishing symbiosis between humans and bifidobacteria. The gene lnpB in the pathway encodes a novel hexosamine kinase NahK, which catalyzes the formation of N-acetylhexosamine 1-phosphate (GlcNAc-1P/GalNAc-1P). In this report, seven three-dimensional structures of NahK in complex with GlcNAc, GalNAc, GlcNAc-1P, GlcNAc/AMPPNP and GlcNAc-1P/ADP from both Bifidobacterium longum (JCM1217) and B. infantis (ATCC15697) were solved at resolutions of 1.5-2.2 Å. NahK is a monomer in solution, and its polypeptide folds in a crescent-like architecture subdivided into two domains by a deep cleft. The NahK structures presented here represent the first multiple reaction complexes of the enzyme. This structural information reveals the molecular basis for the recognition of the given substrates and products, GlcNAc/GalNAc, GlcNAc-1P/GalNAc-1P, ATP/ADP and Mg(2+), and provides insights into the catalytic mechanism, enabling NahK and mutants thereof to form a choice of biocatalysts for enzymatic and chemoenzymatic synthesis of carbohydrates.
authors.affiliation: Genomics Research Center, Academia Sinica, Taipei 115, Taiwan.
authors.forename: Kuei-Chen
authors.initials: KC
authors.lastname: Wang
authors.affiliation: Genomics Research Center, Academia Sinica, Taipei 115, Taiwan.
authors.forename: Syue-Yi
authors.initials: SY
authors.lastname: Lyu
authors.affiliation: Genomics Research Center, Academia Sinica, Taipei 115, Taiwan.
authors.forename: Yu-Chen
authors.initials: YC
authors.lastname: Liu
authors.affiliation: Genomics Research Center, Academia Sinica, Taipei 115, Taiwan.
authors.forename: Chin-Yuan
authors.initials: CY
authors.lastname: Chang
authors.affiliation: Department of Food Science, National Taiwan Ocean University, Keelung 202, Taiwan.
authors.forename: Chang-Jer
authors.initials: CJ
authors.lastname: Wu
authors.affiliation: Genomics Research Center, Academia Sinica, Taipei 115, Taiwan.
authors.forename: Tsung-Lin
authors.initials: TL
authors.lastname: Li
mesh_terms: D000117:Acetylglucosamine / Q000378:metabolism; D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D001644:Bifidobacterium / Q000201:enzymology* / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D008274:Magnesium / Q000378:metabolism; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D010770:Phosphotransferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D013379:Substrate Specificity
chemical_list: D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D010770:Phosphotransferases; D008274:Magnesium; D000117:Acetylglucosamine
keywords: N-acetylhexosamine 1-phosphate kinase; bifidobacteria; multiple reaction complexes