title: Purification and properties of two 2-oxoacid:ferredoxin oxidoreductases from Halobacterium halobium.
abstract: Pyruvate:ferredoxin oxidoreductase and 2-oxoglutarate:ferredoxin oxidoreductase were obtained from cell-free extracts of Halobacterium halobium as homogeneous proteins after ammonium sulfate precipitation, salting-out chromatography with ammonium sulfate on unsubstituted agarose, gel filtration and chromatography on hydroxyapatite. The respective molecular weights are 256000 and 248000. Both enzymes consist of two sets of non-identical subunits of Mr 86000 and 42000 in the case of the pyruvate-degrading enzyme and of 88000 and 36000 in the case of the 20 -oxogluatarate-degrading enzyme. Analyses indicate that an intact enzyme molecule contains two [4 Fe-4S]2 + (2 + , 1+) clusters and two molecules of thiamin diphosphate. Flavin nucleotides, lipoic acid and pantetheine are absent. Thus the enzymes are very similar to the 2-oxoacid:ferredoxin oxidoreductases from fermentative and photosynthetic anaerobes described previously, but are clearly different from the 2-oxoacid dehydrogenase multienzyme complexes which commonly occur in anaerobic organisms.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D004578:Electron Spin Resonance Spectroscopy; D006217:Halobacterium / Q000201:enzymology*; D007656:Ketoglutaric Acids / Q000302:isolation & purification / Q000378:metabolism; D007658:Ketone Oxidoreductases / Q000302:isolation & purification* / Q000378:metabolism; D007700:Kinetics; D008970:Molecular Weight; D050743:Pyruvate Synthase; D011773:Pyruvates / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D000596:Amino Acids; D007656:Ketoglutaric Acids; D011773:Pyruvates; D007658:Ketone Oxidoreductases; D050743:Pyruvate Synthase; C023096:2-oxoglutarate synthase