title: Thermococcus profundus 2-ketoisovalerate ferredoxin oxidoreductase, a key enzyme in the archaeal energy-producing amino acid metabolic pathway.
abstract: 2-Ketoisovalerate ferredoxin oxidoreductase (VOR) is a key enzyme in hyperthermophiles catalyzing the coenzyme A-dependent oxidative decarboxylation of mainly aliphatic amino acid-derived 2-keto acids. The very oxygen-labile enzyme purified under anaerobic conditions from a hyperthermophilic archaeon, Thermococcus profundus, is a hetero-octamer (alphabetagammadelta)(2) consisting of four different subunits, alpha = 45,000, beta = 31,000, gamma = 22,000 and delta = 13,000, respectively. Electron paramagnetic resonance and resonance Raman spectra of the purified enzyme indicate the presence of approximately three [4Fe-4S] clusters per alphabetagammadelta-protomer, although one of the clusters has a tendency to be converted to a [3Fe-4S] form during purification. The optimal temperature for the enzyme activity is 93 +/- 2 degrees C and the cognate [4Fe-4S] ferredoxin serves as an electron acceptor of the enzyme. The purified enzyme is highly oxygen-labile (t(1/2), approximately 5 min at 25 degrees C), and is partly protected in the presence of magnesium ions, thiamine pyrophosphate and sodium chloride (t(1/2), approximately 25 min at 25 degrees C).
authors.affiliation: Department of Life Science and Graduate School of Life Science, and Department of Chemistry and Graduate School of Chemistry, Rikkyo (St. Paul's) University, Toshima-ku, Tokyo 171-8501, Japan.
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Ozawa
authors.forename: Takahiro
authors.initials: T
authors.lastname: Nakamura
authors.forename: Natsu
authors.initials: N
authors.lastname: Kamata
authors.forename: Daisuke
authors.initials: D
authors.lastname: Yasujima
authors.forename: Akio
authors.initials: A
authors.lastname: Urushiyama
authors.forename: Fumiyuki
authors.initials: F
authors.lastname: Yamakura
authors.forename: Daijiro
authors.initials: D
authors.lastname: Ohmori
authors.forename: Takeo
authors.initials: T
authors.lastname: Imai
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D004734:Energy Metabolism / Q000502:physiology*; D007506:Iron-Sulfur Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D007658:Ketone Oxidoreductases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D021122:Protein Subunits / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D019712:Thermococcus / Q000201:enzymology*
chemical_list: D000596:Amino Acids; D007506:Iron-Sulfur Proteins; D021122:Protein Subunits; D007658:Ketone Oxidoreductases; C097621:2-ketoisovalerate ferredoxin oxidoreductase