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Kim, SM, Paek, KH and Lee, SB (2012) Characterization of NADP+-specific L-rhamnose dehydrogenase from the thermoacidophilic Archaeon Thermoplasma acidophilum. Extremophiles 16:447-54

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.

PubMed Online version:10.1007/s00792-012-0444-1

Archaeal Proteins/chemistry; Archaeal Proteins/genetics; Archaeal Proteins/metabolism; Bacterial Proteins/chemistry; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Carbohydrate Dehydrogenases/chemistry; Carbohydrate Dehydrogenases/genetics; Carbohydrate Dehydrogenases/metabolism; Escherichia coli/genetics; Escherichia coli/metabolism; Gene Expression; NADP/chemistry; NADP/genetics; NADP/metabolism; Phylogeny; Recombinant Proteins/chemistry; Recombinant Proteins/genetics; Recombinant Proteins/metabolism; Rhamnose/chemistry; Rhamnose/genetics; Rhamnose/metabolism; Thermoplasma/enzymology; Thermoplasma/genetics