The Physiology and Functional Genomics of Cyanobacterial Hydrogenases and Approaches Towards Biohydrogen Production

Appel, Jens

doi:10.1007/978-94-007-1533-2_15

Cited by 6 publications

(5 citation statements)

References 179 publications

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“…The large surface area represented by the intracellular thylakoids can make this membrane an appropriate place for assembly of the nitrogenase complex, and it might require the hydrogenase for proper function. The possible functions of the uptake hydrogenase have been reviewed recently (5,30), but there is much to be resolved. Biochemical experiments, especially those performed on hydrogenases from Clostridium pasteurianum, indicated that H 2 uptake was inhibited by CO, a known inhibitor of NiFe-hydrogenases (31).…”

Section: Discussionmentioning

confidence: 99%

“…The behavior of this enzyme is dependent on redox conditions: if low-potential electrons are plentiful, Hox is used to pass them on to protons to form H 2 . Under oxidizing conditions, H 2 is split into protons and electrons can again be utilized for metabolism (5). The uptake hydrogenase is composed of small and large subunits, encoded by hupS and hupL, respectively.…”

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confidence: 99%

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The Uptake Hydrogenase in the Unicellular Diazotrophic Cyanobacterium Cyanothece sp. Strain PCC 7822 Protects Nitrogenase from Oxygen Toxicity

Zhang

Sherman²,

Sherman

2014

J Bacteriol

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Cyanothece sp. strain PCC 7822 is a unicellular, diazotrophic cyanobacterium that can produce large quantities of H 2 when grown diazotrophically. This strain is also capable of genetic manipulations and can represent a good model for improving H 2 production from cyanobacteria. To this end, a knockout mutation was made in the hupL gene (⌬hupL), and we determined how this would affect the amount of H 2 produced. The ⌬hupL mutant demonstrated virtually no nitrogenase activity or H 2 production when grown under N 2 -fixing conditions. To ensure that this mutation only affected the hupL gene, a complementation strain was constructed readily with wild-type properties; this indicated that the original insertion was only in hupL. The mutant had no uptake hydrogenase activity but had increased bidirectional hydrogenase (Hox) activity. Western blotting and immunocytochemistry under the electron microscope indicated that the mutant had neither HupL nor NifHDK, although the nif genes were transcribed. Interestingly, biochemical analysis demonstrated that both HupL and NifH could be membrane associated. The results indicated that the nif genes were transcribed but that NifHDK was either not translated or was translated but rapidly degraded. We hypothesized that the Nif proteins were made but were unusually susceptible to O 2 damage. Thus, we grew the mutant cells under anaerobic conditions and found that they grew well under N 2 -fixing conditions. We conclude that in unicellular diazotrophs, like Cyanothece sp. strain PCC 7822, the HupLS complex helps remove oxygen from the nitrogenase, and that this is a more important function than merely oxidizing the H 2 produced by the nitrogenase.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

The Uptake Hydrogenase in the Unicellular Diazotrophic Cyanobacterium Cyanothece sp. Strain PCC 7822 Protects Nitrogenase from Oxygen Toxicity

Zhang

Sherman²,

Sherman

2014

J Bacteriol

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“…NAD(P)-linked Hox hydrogenases have been identified and characterized in cyanobacteria (4,5), the Gram-positive bacterium Rhodococcus opacus (7,8), the Gram-negative bacterium Ralstonia eutropha (6), and the purple sulfur photosynthetic bacteria Thiocapsa roseopersicina and Allochromatium vinosum (9 -12). These Hox hydrogenases are multimeric with at least four related subunits expressed from a single operon.…”

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Genetic Analysis of the Hox Hydrogenase in the Cyanobacterium Synechocystis sp. PCC 6803 Reveals Subunit Roles in Association, Assembly, Maturation, and Function

Eckert

Boehm

Carrieri

et al. 2012

Journal of Biological Chemistry

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Background: Hox hydrogenase (HoxEFUYH) is present in some bacteria and cyanobacteria. Results: In Synechocystis, HoxYH and HoxEFU form subcomplexes that can be disrupted in Hox subunit mutants. Conclusion: Hox assembly is modular and most reliant on the presence of HoxF and -U, consistent with effects on Hox protein abundance and activity. Significance: Subcomplexes of Hox hydrogenase may represent steps in complex assembly and maturation.

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“…Additionally, despite the fact that [NiFe]-hydrogenases have been phylogenetically divided into four distinct groups, all of the established model systems are representatives of the “uptake”, also known as group 1, class, a group of heterodimeric, monofunctional enzymes thought to catalyze hydrogen oxidation in vivo . However, two functionally distinct [NiFe]-hydrogenases are present in the cyanobacteria, an uptake and a bidirectional enzyme, and the latter is thought to interact with photosynthetic pathways. − Enzymes of the cytoplasmic, bidirectional group of [NiFe]-hydrogenases have been much less studied than those from the uptake group. They are hetero-multimeric, bifunctional enzymes usually coupling proton/hydrogen interconversion at the [NiFe] active site with NAD(P) reduction at a flavin mononucleotide active site.…”

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The [NiFe]-Hydrogenase of the Cyanobacterium Synechocystis sp. PCC 6803 Works Bidirectionally with a Bias to H₂ Production

et al. 2011

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Protein film electrochemistry (PFE) was utilized to characterize the catalytic activity and oxidative inactivation of a bidirectional [NiFe]-hydrogenase (HoxEFUYH) from the cyanobacterium Synechocystis sp. PCC 6803. PFE provides precise control of the redox potential of the adsorbed enzyme so that its activity can be monitored under changing experimental conditions as current. The properties of HoxEFUYH are different from those of both the standard uptake and the "oxygen-tolerant" [NiFe]-hydrogenases. First, HoxEFUYH is biased toward proton reduction as opposed to hydrogen oxidation. Second, despite being expressed under aerobic conditions in vivo, HoxEFUYH is clearly not oxygen-tolerant. Aerobic inactivation of catalytic hydrogen oxidation by HoxEFUYH is total and nearly instantaneous, producing two inactive states. However, unlike the Ni-A and Ni-B inactive states of standard [NiFe]-hydrogenases, both of these states are quickly (<90 s) reactivated by removal of oxygen and exposure to reducing conditions. Third, proton reduction continues at 25-50% of the maximal rate in the presence of 1% oxygen. Whereas most previously characterized [NiFe]-hydrogenases seem to be preferential hydrogen oxidizing catalysts, the cyanobacterial enzyme works effectively in both directions. This unusual catalytic bias as well as the ability to be quickly reactivated may be essential to fulfilling the physiological role in cyanobacteria, organisms expected to experience swings in cellular reduction potential as they switch between aerobic conditions in the light and dark anaerobic conditions. Our results suggest that the uptake [NiFe]-hydrogenases alone are not representative of the catalytic diversity of [NiFe]-hydrogenases, and the bidirectional heteromultimeric enzymes may serve as valuable models to understand the diverse mechanisms of tuning the reactivity of the hydrogen activating site.

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The Physiology and Functional Genomics of Cyanobacterial Hydrogenases and Approaches Towards Biohydrogen Production

Cited by 6 publications

References 179 publications

The Uptake Hydrogenase in the Unicellular Diazotrophic Cyanobacterium Cyanothece sp. Strain PCC 7822 Protects Nitrogenase from Oxygen Toxicity

The Uptake Hydrogenase in the Unicellular Diazotrophic Cyanobacterium Cyanothece sp. Strain PCC 7822 Protects Nitrogenase from Oxygen Toxicity

Genetic Analysis of the Hox Hydrogenase in the Cyanobacterium Synechocystis sp. PCC 6803 Reveals Subunit Roles in Association, Assembly, Maturation, and Function

The [NiFe]-Hydrogenase of the Cyanobacterium Synechocystis sp. PCC 6803 Works Bidirectionally with a Bias to H₂ Production

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The Physiology and Functional Genomics of Cyanobacterial Hydrogenases and Approaches Towards Biohydrogen Production

Cited by 6 publications

References 179 publications

The Uptake Hydrogenase in the Unicellular Diazotrophic Cyanobacterium Cyanothece sp. Strain PCC 7822 Protects Nitrogenase from Oxygen Toxicity

The Uptake Hydrogenase in the Unicellular Diazotrophic Cyanobacterium Cyanothece sp. Strain PCC 7822 Protects Nitrogenase from Oxygen Toxicity

Genetic Analysis of the Hox Hydrogenase in the Cyanobacterium Synechocystis sp. PCC 6803 Reveals Subunit Roles in Association, Assembly, Maturation, and Function

The [NiFe]-Hydrogenase of the Cyanobacterium Synechocystis sp. PCC 6803 Works Bidirectionally with a Bias to H2 Production

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The [NiFe]-Hydrogenase of the Cyanobacterium Synechocystis sp. PCC 6803 Works Bidirectionally with a Bias to H₂ Production