title: The dihydrolipoamide dehydrogenase from the crenarchaeon Acidianus ambivalens.
abstract: A dihydrolipoamide dehydrogenase (DLDH) was purified and characterized for the first time from a crenarchaeon, Acidianus ambivalens. The holoenzyme consists of two identical subunits with a molecular mass of 45.4 kDa per monomer. It contains FAD as a prosthetic group and uses NAD+ as the preferential substrate, but can also reduce NADP+. The Michaelis-Menten constants of the forward (NAD+ reduction) and reverse (NADH oxidation) reactions were KM (dihydrolipoamide)=0.70 mM, KM (NAD+)=0.71 mM, KM (lipoamide)=1.26 mM and KM (NADH)=3.15 microM. A comparative study of NADH:lipoamide oxidoreductase and NADH:K3[Fe(CN)6] oxidoreductase activities was performed, the optimal temperature and pH being different for each: 55 degrees C, pH 7 and 89 degrees C, pH 5.5, respectively. Although DLDH is generally part of the alpha-ketoacid dehydrogenase complexes in Bacteria and Eukarya, none of these complexes has yet been isolated from Sulfolobales. The metabolic role of DLDH in these organisms is discussed.
authors.affiliation: Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal.
authors.forename: Ana P
authors.initials: AP
authors.lastname: Batista
authors.forename: Arnulf
authors.initials: A
authors.lastname: Kletzin
authors.forename: Manuela M
authors.initials: MM
authors.lastname: Pereira
mesh_terms: D041541:Acidianus / Q000201:enzymology* / Q000235:genetics; D019843:Archaeal Proteins / Q000737:chemistry* / Q000302:isolation & purification; D008058:Dihydrolipoamide Dehydrogenase / Q000737:chemistry* / Q000302:isolation & purification; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D020539:Sequence Analysis, Protein; D013057:Spectrum Analysis; D013696:Temperature
chemical_list: D019843:Archaeal Proteins; D008058:Dihydrolipoamide Dehydrogenase