Publications

• Escherichia coli pyruvate:flavodoxin oxidoreductase, YdbK - regulation of expression and biological roles in protection against oxidative stress.

  Nakayama T., Yonekura S., Yonei S., Zhang-Akiyama Q.M.

  E. coli YdbK is predicted to be a pyruvate:flavodoxin oxidoreductase (PFOR). However, enzymatic activity and the regulation of gene expression of it are not well understood. In this study, we found that E. coli cells overexpressing the ydbK gene had enhanced PFOR activity, indicating the product o ... >> More

  E. coli YdbK is predicted to be a pyruvate:flavodoxin oxidoreductase (PFOR). However, enzymatic activity and the regulation of gene expression of it are not well understood. In this study, we found that E. coli cells overexpressing the ydbK gene had enhanced PFOR activity, indicating the product of ydbK to be a PFOR. The PFOR was labile to oxygen. The expression of ydbK was induced by superoxide generators such as methyl viologen (MV) in a SoxS-dependent manner after a lag period. We identified a critical element upstream of ydbK gene required for the induction by MV and proved direct binding of SoxS to the element. E. coli ydbK mutant was highly sensitive to MV, which was enhanced by additional inactivation of fpr gene encoding ferredoxin (flavodoxin):NADP(H) reductase (FPR). Aconitase activity, a superoxide sensor, was more extensively decreased by MV in the E. coli ydbK mutant than in wild-type strain. The induction level of soxS gene was higher in E. coli ydbK fpr double mutant than in wild-type strain. These results indicate that YdbK helps to protect cells from oxidative stress. It is possible that YdbK maintains the cellular redox state together with FPR and is involved in the reduction of oxidized proteins including SoxR in the late stages of the oxidative stress response in E. coli. << Less

  Genes Genet Syst 88:175-188(2013) [PubMed] [EuropePMC]

• Electron transport to nitrogenase. Purification and characterization of pyruvate:flavodoxin oxidoreductase. The nifJ gene product.

  Shah V.K., Stacey G., Brill W.J.

  Pyruvate:flavodoxin oxidoreductase, the nifJ gene product of Klebsiella pneumoniae, was purified to homogeneity. Pyruvate:flavodoxin oxidoreductase, flavodoxin, and nitrogenase components I and II are the only proteins required for pyruvate-coupled nitrogenase activity. The physiological source of ... >> More

  Pyruvate:flavodoxin oxidoreductase, the nifJ gene product of Klebsiella pneumoniae, was purified to homogeneity. Pyruvate:flavodoxin oxidoreductase, flavodoxin, and nitrogenase components I and II are the only proteins required for pyruvate-coupled nitrogenase activity. The physiological source of electrons to nitrogenase in K. pneumoniae is pyruvate. Flavodoxin from Azotobacter vinelandii was only one-third as effective as K. pneumoniae flavodoxin in transferring electrons from pyruvate:flavodoxin oxidoreductase to Azotobacter and Klebsiella nitrogenases. Ferredoxins from aerobic, anaerobic and photosynthetic nitrogen-fixing organisms, as well as benzyl viologen and methyl viologen, were ineffective in coupling pyruvate oxidation to nitrogenase activity. One mol each of acetyl-CoA, CO2, and ethylene are formed by pyruvate-supported acetylene reduction. The enzyme contains 8.0 +/-0.6 mol of iron and 6.6 +/-0.2 mol of acid-labile sulfide per mol of protein (Mr = 240,000). Pyruvate:flavodoxin oxidoreductase is irreversibly inactivated by air. << Less

  J Biol Chem 258:12064-12068(1983) [PubMed] [EuropePMC]

• Routes of flavodoxin and ferredoxin reduction in Escherichia coli. CoA-acylating pyruvate: flavodoxin and NADPH: flavodoxin oxidoreductases participating in the activation of pyruvate formate-lyase.

  Blaschkowski H.P., Neuer G., Ludwig-Festl M., Knappe J.

  Flavodoxin and ferredoxin become reduced in Escherichia coli cells by oxidoreductase reactions which use pyruvate and NADPH as electron donor substrates. The two enzymes, which are minor proteins of this organism, were measured through the reduced flavodoxin-dependent activation of pyruvate format ... >> More

  Flavodoxin and ferredoxin become reduced in Escherichia coli cells by oxidoreductase reactions which use pyruvate and NADPH as electron donor substrates. The two enzymes, which are minor proteins of this organism, were measured through the reduced flavodoxin-dependent activation of pyruvate formate-lyase. The NADPH-dependent enzyme, obtained homogeneously through Procion-red affinity chromatography, was identified as the flavoprotein 'component R' described previously by Fujii and Huennekens [J. Biol. Chem. 249, 6745-6753 (1974)]. The pyruvate-dependent enzyme was identified as CoA-acetylating pyruvate:flavodoxin (ferredoxin) oxidoreductase. Its catalytic properties in the forward, reverse, and the 14CO2-pyruvate exchange reaction are reported. The dihydro form of flavodoxin was characterized as the particular species involved in the activation of pyruvate formate-lyase. The activation process still occurs with 70% of maximal efficiency when the ratio [NADPH]/([NADP] + [NADPH]) is fixed at the intracellular 'anabolic reduction charge' value of 0.45, in conjunction with the NADPH-dependent enzyme. The [2Fe-2S] ferredoxin, though being readily used as electron acceptor of both oxidoreductases and having a redox potential similar to flavodoxin, proved incompetent in mediating the activation of pyruvate formate-lyase. << Less

  Eur. J. Biochem. 123:563-569(1982) [PubMed] [EuropePMC]

• Helicobacter pylori porCDAB and oorDABC genes encode distinct pyruvate:flavodoxin and 2-oxoglutarate:acceptor oxidoreductases which mediate electron transport to NADP.

  Hughes N.J., Clayton C.L., Chalk P.A., Kelly D.J.

  Helicobacter pylori, a major cause of human gastric disease, is a microaerophilic bacterium that contains neither pyruvate nor 2-oxoglutarate dehydrogenase activity. Previous studies (N. J. Hughes, P. A. Chalk, C. L. Clayton, and D. J. Kelly, J. Bacteriol. 177:3953-3959, 1995) have indicated that ... >> More

  Helicobacter pylori, a major cause of human gastric disease, is a microaerophilic bacterium that contains neither pyruvate nor 2-oxoglutarate dehydrogenase activity. Previous studies (N. J. Hughes, P. A. Chalk, C. L. Clayton, and D. J. Kelly, J. Bacteriol. 177:3953-3959, 1995) have indicated that the major routes for the generation of acetyl coenzyme A (acetyl-CoA) and succinyl-CoA are via pyruvate:flavodoxin oxidoreductase (POR) and 2-oxoglutarate:acceptor oxidoreductase (OOR), respectively. The purified POR is a heterotetrameric protein, with subunits of 48 (PorA), 36 (PorB), 24 (PorC), and 14 (PorD) kDa. In this study OOR has been purified, and it is similarly composed of polypeptides of 43 (OorA), 33 (OorB), 24 (OorC), and 10 (OorD) kDa. Both POR and OOR are oxygen labile and are likely to be major contributors to the microaerophilic phenotype of H. pylori. Unlike POR, OOR was unable to use a previously identified flavodoxin (FldA) as an electron acceptor. Although the purified enzymes were unable to reduce NAD(P), electrons from both pyruvate and 2-oxoglutarate could reduce NADP in cell extracts, consistent with a role for these oxidoreductases in the provision of NADPH as a respiratory electron donor. The H. pylori por, oor, and fldA genes were cloned and sequenced. The deduced por gene products showed significant sequence similarity to archaeal four-subunit 2-oxoacid:acceptor oxidoreductases. However, the amino acid sequences of OorA and -B were more closely related to that of the two-subunit POR of the aerobic halophile Halobacterium halobium. Both porD and oorD encode integral ferredoxin-like subunits. POR and OOR are probably essential enzymes in H. pylori, as insertion inactivation of porB and oorA appeared to be lethal. << Less

  J Bacteriol 180:1119-1128(1998) [PubMed] [EuropePMC]