title: Characterization of NADP+-specific L-rhamnose dehydrogenase from the thermoacidophilic Archaeon Thermoplasma acidophilum.
abstract: Thermoplasma acidophilum utilizes L-rhamnose as a sole carbon source. To determine the metabolic pathway of L-rhamnose in Archaea, we identified and characterized L-rhamnose dehydrogenase (RhaD) in T. acidophilum. Ta0747P gene, which encodes the putative T. acidophilum RhaD (Ta_RhaD) enzyme belonging to the short-chain dehydrogenase/reductase family, was expressed in E. coli as an active enzyme catalyzing the oxidation of L-rhamnose to L-rhamnono-1,4-lactone. Analysis of catalytic properties revealed that Ta_RhaD oxidized L-rhamnose, L-lyxose, and L-mannose using only NADP(+) as a cofactor, which is different from NAD(+)/NADP(+)-specific bacterial RhaDs and NAD(+)-specific eukaryal RhaDs. Ta_RhaD showed the highest activity toward L-rhamnose at 60 °C and pH 7. The K (m) and k (cat) values were 0.46 mM, 1,341.3 min(-1) for L-rhamnose and 0.1 mM, 1,027.2 min(-1) for NADP(+), respectively. Phylogenetic analysis indicated that branched lineages of archaeal RhaD are quite distinct from those of Bacteria and Eukarya. This is the first report on the identification and characterization of NADP(+)-specific RhaD.
authors.affiliation: Department of Chemical Engineering, Pohang University of Science and Technology, San 31, Hyoja Dong, Pohang, 790-784, Korea.
authors.forename: Suk Min
authors.initials: SM
authors.lastname: Kim
authors.forename: Kwang Hyun
authors.initials: KH
authors.lastname: Paek
authors.forename: Sun Bok
authors.initials: SB
authors.lastname: Lee
mesh_terms: D019843:Archaeal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D002237:Carbohydrate Dehydrogenases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D009249:NADP / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012210:Rhamnose / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013822:Thermoplasma / Q000201:enzymology* / Q000235:genetics
chemical_list: D019843:Archaeal Proteins; D001426:Bacterial Proteins; D011994:Recombinant Proteins; D009249:NADP; D002237:Carbohydrate Dehydrogenases; C022524:L-rhamnose dehydrogenase; D012210:Rhamnose