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Characterization of NADH oxidase/NADPH polysulfide oxidoreductase and its unexpected participation in oxygen sensitivity in an anaerobic hyperthermophilic archaeon.

ABSTRACT: Many genomes of anaerobic hyperthermophiles encode multiple homologs of NAD(P)H oxidase that are thought to function in response to oxidative stress. We investigated one of the seven NAD(P)H oxidase homologs (TK1481) in the sulfur-reducing hyperthermophilic archaeon Thermococcus kodakarensis, focusing on the catalytic properties and roles in oxidative-stress defense and sulfur-dependent energy conservation. The recombinant form of TK1481 exhibited both NAD(P)H oxidase and NAD(P)H:polysulfide oxidoreductase activities. The enzyme also possessed low NAD(P)H peroxidase and NAD(P)H:elemental sulfur oxidoreductase activities under anaerobic conditions. A mutant form of the enzyme, in which the putative redox-active residue Cys43 was replaced by Ala, still showed NADH-dependent flavin adenine dinucleotide (FAD) reduction activity. Although it also retained successive oxidase and anaerobic peroxidase activities, the ability to reduce polysulfide and sulfur was completely lost, suggesting the specific reactivity of the Cys43 residue for sulfur. To evaluate the physiological function of TK1481, we constructed a gene deletant, ?TK1481, and mutant KUTK1481C43A, into which two base mutations altering Cys43 of TK1481 to Ala were introduced. ?TK1481 exhibited growth properties nearly identical to those of the parent strain, KU216, in sulfur-containing media. Interestingly, in the absence of elemental sulfur, the growth of ?TK1481 was not affected by dissolved oxygen, whereas the growth of KU216 and KUTK1481C43A was significantly impaired. These results indicate that although TK1481 does not play a critical role in either sulfur reduction or the response to oxidative stress, the NAD(P)H oxidase activity of TK1481 unexpectedly participates in the oxygen sensitivity of the hyperthermophilic archaeon T. kodakarensis in the absence of sulfur.

SUBMITTER: Kobori H

PROVIDER: S-EPMC2944514 | biostudies-literature | 2010 Oct

REPOSITORIES: biostudies-literature

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Characterization of NADH oxidase/NADPH polysulfide oxidoreductase and its unexpected participation in oxygen sensitivity in an anaerobic hyperthermophilic archaeon.

Kobori Hiroki H Ogino Masayuki M Orita Izumi I Nakamura Satoshi S Imanaka Tadayuki T Fukui Toshiaki T

Journal of bacteriology 20100730 19

Many genomes of anaerobic hyperthermophiles encode multiple homologs of NAD(P)H oxidase that are thought to function in response to oxidative stress. We investigated one of the seven NAD(P)H oxidase homologs (TK1481) in the sulfur-reducing hyperthermophilic archaeon Thermococcus kodakarensis, focusing on the catalytic properties and roles in oxidative-stress defense and sulfur-dependent energy conservation. The recombinant form of TK1481 exhibited both NAD(P)H oxidase and NAD(P)H:polysulfide oxi ...[more]

PMID: 20675490

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Project description:BACKGROUND:Water-forming NADH oxidase can oxidize cytosolic NADH to NAD(+), thus relieving cytosolic NADH accumulation in Saccharomyces cerevisiae. Previous studies of the enzyme were conducted under aerobic conditions, as O2 is the recognized electron acceptor of the enzyme. In order to extend its use in industrial production and to study its effect on anaerobes, the effects of overexpression of this oxidase in S. cerevisiae BY4741 and Clostridium acetobutylicum 428 (Cac-428) under anaerobic conditions were evaluated. RESULTS:Glucose was exhausted in the NADH oxidase-overexpressing S. cerevisiae strain (Sce-NOX) culture after 26 h, while 43.51 ± 2.18 g/L residual glucose was left in the control strain (Sce-CON) culture at this time point. After 30 h of fermentation, the concentration of ethanol produced by Sce-NOX reached 36.28 ± 1.81 g/L, an increase of 56.38 % as compared to Sce-CON (23.20 ± 1.16 g/L), while the byproduct glycerol was remarkably decreased in the culture of Sce-NOX. In the case of the C. acetobutylicum strain (Cac-NOX) overexpressing NADH oxidase, glucose consumption, cell growth rate, and the production of acetone-butanol-ethanol (ABE) all decreased, while the concentrations of acetic acid and butyric acid increased as compared to the control strain (Cac-CON). During fermentation of Cac-CON and Cac-NOX in 100-mL screw-capped bottles, the concentrations of ABE increased with increasing headspace. Additionally, several alternative electron acceptors in C. acetobutylicum fermentation were tested. Nitroblue tetrazolium and 2,6-dichloroindophenol were lethiferous to both Cac-CON and Cac-NOX. Methylene blue could relieve the effect caused by the overexpression of the NADH oxidase on the metabolic network of C. acetobutylicum strains, while cytochrome c aggravated the effect. CONCLUSIONS:The water-forming NADH oxidase could regulate the metabolism of both the S. cerevisiae and the C. acetobutylicum strains in anaerobic conditions. Thus, the recombinant S. cerevisiae strain might be useful in industrial production. Besides the recognized electron acceptor O2, methylene blue and/or the structural analogs may be the alternative elector acceptor of the NADH oxidase in anaerobic conditions.

Dataset Information

Characterization of NADH oxidase/NADPH polysulfide oxidoreductase and its unexpected participation in oxygen sensitivity in an anaerobic hyperthermophilic archaeon.

Publications

Characterization of NADH oxidase/NADPH polysulfide oxidoreductase and its unexpected participation in oxygen sensitivity in an anaerobic hyperthermophilic archaeon.

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