title: Analysis of plant UDP-arabinopyranose mutase (UAM): Role of divalent metals and structure prediction.
abstract: UDP-arabinopyranose mutase (UAM) is a plant enzyme which interconverts UDP-arabinopyranose (UDP-Arap; a six-membered sugar) to UDP-arabinofuranose (UDP-Araf; a five-membered sugar). Plant mutases belong to a small gene family called Reversibly Glycosylated Proteins (RGPs). So far, UAM has been identified in Oryza sativa (Rice), Arabidopsis thaliana and Hordeum vulgare (Barley). The enzyme requires divalent metal ions for catalytic activity. Here, the divalent metal ion dependency of UAMs from O. sativa (rice) and A. thaliana have been studied using HPLC-based kinetic assays. It was determined that UAM from these species had the highest relative activity in a range of 40-80μM Mn2+. Excess Mn2+ ion concentration decreased the enzyme activity. This trend was observed when other divalent metal ions were used to test activity. To gain a perspective of the role played by the metal ion in activity, an ab initio structural model was generated based on the UAM amino acid sequence and a potential metal binding region was identified. Based on our results, we propose that the probable role of the metal in UAM is stabilizing the diphosphate of the substrate, UDP-Arap.
authors.affiliation: Department of Chemistry, University of Saskatchewan, 110 Science Place, Saskatoon, Saskatchewan, S7N 5C9, Canada.
authors.forename: Jijin R A
authors.initials: JRA
authors.lastname: Kuttiyatveetil
authors.affiliation: Department of Chemistry, University of Saskatchewan, 110 Science Place, Saskatoon, Saskatchewan, S7N 5C9, Canada. Electronic address: david.sanders@usask.ca.
authors.forename: David A R
authors.initials: DAR
authors.lastname: Sanders
mesh_terms: D017360:Arabidopsis / Q000201:enzymology*; D001665:Binding Sites; D002384:Catalysis; D002473:Cell Wall / Q000201:enzymology; D018506:Gene Expression Regulation, Plant; D019751:Intramolecular Transferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D007477:Ions / Q000737:chemistry; D007700:Kinetics; D008670:Metals / Q000737:chemistry; D012275:Oryza / Q000201:enzymology*; D011485:Protein Binding; D014539:Uridine Diphosphate Sugars / Q000737:chemistry* / Q000378:metabolism
chemical_list: D007477:Ions; D008670:Metals; D014539:Uridine Diphosphate Sugars; C040817:uridine diphosphate arabinose; D019751:Intramolecular Transferases
keywords: Enzyme kinetics; L-arabinofuranose; Metalloproteins; Plant mutase; Reversibly glycosylated polypeptides; Structure prediction; UDP-arabinopyranose mutase