title: Heterogeneity of quaternary structure of glucosamine-6-phosphate deaminase from Giardia lamblia.
abstract: The oligoHis-tagged versions of glucosamine-6-phosphate deaminase from Giardia lamblia (GlmNagB-HisN, GlmNagB-HisC) were constructed and purified to hear homogeneity, and their kinetic and structural properties were compared to those of the wild-type enzyme (GlmNagB). Introduction of the oligoHis tag at the GlmNagB C-terminus resulted in almost complete loss of the catalytic activity, while the catalytic properties of GlmNagB-HisN and GlmNagB were very similar. The recombinant and wild-type enzyme exhibits heterogeneity of the quaternary structure and in solution exists in three interconvertible forms, namely, monomeric, homodimeric, and homotetrameric. Although the monomeric form is prevalent, the monomer/dimer/tetramer ratios depended on protein concentration and fell within the range from 72:27:1 to 39:23:38. The enzyme is fully active in each of the oligomeric structures, efficiently catalyzes synthesis of D-glucosamine-6-phosphate from D-fructose-6-phosphate and ammonia, and its activity is not modified by GlcNAc6P, UDP-GlcNAc, or UDP-GalNAc. GlcN6P deaminase of G. lamblia represents a novel structural and functional type of enzyme of the NagB subfamily.
authors.affiliation: Department of Pharmaceutical Technology and Biochemistry, Gdańsk University of Technology, 11/12 Narutowicza Str., 80-233, Gdańsk, Poland.
authors.forename: Karolina
authors.initials: K
authors.lastname: Kwiatkowska-Semrau
authors.forename: Justyna
authors.initials: J
authors.lastname: Czarnecka
authors.forename: Marek
authors.initials: M
authors.lastname: Wojciechowski
authors.forename: Sławomir
authors.initials: S
authors.lastname: Milewski
mesh_terms: D000117:Acetylglucosamine / Q000031:analogs & derivatives / Q000378:metabolism; D019747:Aldose-Ketose Isomerases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli; D005636:Fructosephosphates / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D016829:Giardia lamblia / Q000201:enzymology*; D005944:Glucosamine / Q000031:analogs & derivatives / Q000378:metabolism; D019298:Glucose-6-Phosphate / Q000031:analogs & derivatives / Q000378:metabolism; D011487:Protein Conformation
chemical_list: D005636:Fructosephosphates; C010004:N-acetylglucosamine 6-phosphate; C001293:glucosamine 6-phosphate; D019298:Glucose-6-Phosphate; C027618:fructose-6-phosphate; C020582:glucosamine-6-phosphate isomerase; D019747:Aldose-Ketose Isomerases; D005944:Glucosamine; D000117:Acetylglucosamine