title: Crystal structure of uridine-diphospho-N-acetylglucosamine pyrophosphorylase from Candida albicans and catalytic reaction mechanism.
abstract: Uridine-diphospho-N-acetylglucosamine (UDP-GlcNAc) is a precursor of the bacterial and fungal cell wall. It is also used in a component of N-linked glycosylation and the glycosylphosphoinositol anchor of eukaryotic proteins. It is synthesized from N-acetylglucosamine-1-phosphate (GlcNAc-1-P) and uridine-5'-triphosphate (UTP) by UDP-GlcNAc pyrophosphorylase (UAP). This is an S(N)2 reaction; the non-esterified oxygen atom of the GlcNAc-1-P phosphate group attacks the alpha-phosphate group of UTP. We determined crystal structures of UAP from Candida albicans (CaUAP1) without any ligands and also complexed with its substrate or with its product. The series of structures in different forms shows the induced fit movements of CaUAP1. Three loops approaching the ligand molecule close the active site when ligand is bound. In addition, Lys-421, instead of the metal ion in prokaryotic UAPs, is coordinated by both phosphate groups of UDP-Glc-NAc and acts as a cofactor. However, a magnesium ion enhances the enzymatic activity of CaUAP1, and thus we propose that the magnesium ion increases the affinity between UTP and the enzyme by coordinating to the alpha- and gamma-phosphate group of UTP.
authors: Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
authors: Daisuke
authors: D
authors: Maruyama
authors: Yuichi
authors: Y
authors: Nishitani
authors: Tsuyoshi
authors: T
authors: Nonaka
authors: Akiko
authors: A
authors: Kita
authors: Takaaki A
authors: TA
authors: Fukami
authors: Toshiyuki
authors: T
authors: Mio
authors: Hisafumi
authors: H
authors: Yamada-Okabe
authors: Toshiko
authors: T
authors: Yamada-Okabe
authors: Kunio
authors: K
authors: Miki
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002176:Candida albicans / Q000201:enzymology*; D002384:Catalysis; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009713:Nucleotidyltransferases / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid
chemical_list: D009713:Nucleotidyltransferases; C023226:UDPacetylglucosamine pyrophosphorylase