title: Pyruvate:quinone oxidoreductase from Corynebacterium glutamicum: purification and biochemical characterization.
abstract: Pyruvate:quinone oxidoreductase catalyzes the oxidative decarboxylation of pyruvate to acetate and CO2 with a quinone as the physiological electron acceptor. So far, this enzyme activity has been found only in Escherichia coli. Using 2,6-dichloroindophenol as an artificial electron acceptor, we detected pyruvate:quinone oxidoreductase activity in cell extracts of the amino acid producer Corynebacterium glutamicum. The activity was highest (0.055 +/- 0.005 U/mg of protein) in cells grown on complex medium and about threefold lower when the cells were grown on medium containing glucose, pyruvate, or acetate as the carbon source. From wild-type C. glutamicum, the pyruvate:quinone oxidoreductase was purified about 180-fold to homogeneity in four steps and subjected to biochemical analysis. The enzyme is a flavoprotein, has a molecular mass of about 232 kDa, and consists of four identical subunits of about 62 kDa. It was activated by Triton X-100, phosphatidylglycerol, and dipalmitoyl-phosphatidylglycerol, and the substrates were pyruvate (kcat=37.8 +/- 3 s(-1); Km=30 +/- 3 mM) and 2-oxobutyrate (kcat=33.2 +/- 3 s(-1); Km=90 +/- 8 mM). Thiamine pyrophosphate (Km=1 microM) and certain divalent metal ions such as Mg2+ (Km=29 microM), Mn2+ (Km=2 microM), and Co2+ (Km=11 microM) served as cofactors. In addition to several dyes (2,6-dichloroindophenol, p-iodonitrotetrazolium violet, and nitroblue tetrazolium), menadione (Km=106 microM) was efficiently reduced by the purified pyruvate:quinone oxidoreductase, indicating that a naphthoquinone may be the physiological electron acceptor of this enzyme in C. glutamicum.
authors.affiliation: Department of Microbiology and Biotechnology, University of Ulm, 89069 Ulm, Germany.
authors.forename: Mark E
authors.initials: ME
authors.lastname: Schreiner
authors.forename: Bernhard J
authors.initials: BJ
authors.lastname: Eikmanns
mesh_terms: D000445:Aldehyde Oxidoreductases / Q000302:isolation & purification* / Q000378:metabolism*; D000595:Amino Acid Sequence; D017124:Conserved Sequence; D048230:Corynebacterium glutamicum / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D004795:Enzyme Stability; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014461:Ultracentrifugation
chemical_list: D000445:Aldehyde Oxidoreductases; C496833:pyruvate quinone oxidoreductase