Inhibition of nitrogenase-catalyzed reductions

Hwang, Jeemin; Chen, C.H.; Burris, R. H.

doi:10.1016/0005-2728(73)90270-3

Cited by 181 publications

(146 citation statements)

References 21 publications

Supporting

Mentioning

123

Contrasting

Order By: Relevance

“…However, we do not wish to imply that the oxidation state of the metal atoms or conformation of this site is the same for the enzyme-substrate (acetylene) and enzyme-product (ethylene) complexes. A separate high-affinity CO-binding site has been assumed, since CO is a non-competitive inhibitor of acetylene reduction (Hwang et al, 1973). We have omitted a number of equilibria in both schemes for the sake of clarity and do not imply, for instance, that CO only binds when acetylene is also bound at the other site, as in species (i) (Scheme 2).…”

Section: Epr Signals Under Ar Plus Ethylenementioning

confidence: 99%

Electron-paramagnetic-resonance studies on nitrogenase of Klebsiella pneumoniae. Evidence for acetylene- and ethylene-nitrogenase transient complexes

Lowe¹,

Eady²,

Thorneley³

1978

Biochemical Journal

View full text Add to dashboard Cite

Klebsiella pneumoniae nitrogenase exhibited four new electron-paramagnetic-resonance signals during turnover at 10 degrees C, pH7.4, which were assigned to intermediates present in low concentrations in the steady state. 57Fe-substituted Mo–Fe protein showed that they arose from Fe–S clusters in the Mo–Fe protein of nitrogenase. The new signals are designated: Ic, g values at 4.67, 3.37 and approx. 2.0; VI, g values at 2.125, 2.000 and 2.000; VII, g values at 5.7 and 5.4; VIII, g values at 2.092, 1.974 and 1.933. The sharp axial signal VI arises from a Fe4S4 cluster at the −1 oxidation level. This signal was only detected in the presence of ethylene and provides the first evidence of an enzyme–product complex for nitrogenase. [13C]Acetylene and [13C]ethylene provided no evidence for direct binding of this substrate and product to the Fe–S clusters giving rise to these signals. The dependence of signal intensities on acetylene concentration indicated two types of binding site, with apparent dissociation constants K less than 16 micron and K approximately 13mM. A single binding site for ethylene (K=1.5mM) was detected. A scheme is proposed for the mechanism of reduction of acetylene to ethylene and inhibition of this reaction by CO.

show abstract

Section: Epr Signals Under Ar Plus Ethylenementioning

confidence: 99%

Electron-paramagnetic-resonance studies on nitrogenase of Klebsiella pneumoniae. Evidence for acetylene- and ethylene-nitrogenase transient complexes

Lowe¹,

Eady²,

Thorneley³

1978

Biochemical Journal

View full text Add to dashboard Cite

show abstract

“…During this process, which occurs at substantial rates even when nitrogen is saturating (11,12), about four molecules of ATP are 1207 hydrolyzed per H2 produced (13)(14)(15). Although H2 evolution has been observed from detached nodules of some legumes (16)(17)(18)(19)(20), it has been suggested that no net ATP-dependent production of hydrogen via nitrogenase occurs in vivo (5).…”

Section: Introductionmentioning

confidence: 99%

Hydrogen evolution: A major factor affecting the efficiency of nitrogen fixation in nodulated symbionts

Schubert

Evans

1976

Proc. Natl. Acad. Sci. U.S.A.

444

276

View full text Add to dashboard Cite

Nitrogenase-dependent hydrogen evolution from detached legume nodules and from reaction mixtures containing cell-free nitrogenase has been well established, but the overall effect of hydrogen evolution on the efficiency of nitrogen fixation in vivo has not been critically assessed. This paper describes a survey which revealed that hydrogen evolution is a general phenomenon associated with nitrogen fixation by many nodulated nitrogen-fixing symbionts. An evaluation of the magnitude of energy loss in terms of the efficiency of electron transfer to nitrogen, via nitirogenase, in excised nodules suggested that hydrogen production may severely reduce nitrogen fixation in many legumes where photosynthate supply is a factor limiting fixation. With most symbionts. including soybeans, only 40-60% of the electron fow to nitrogenase was transferred to nitrogen. The remainder was lost through hydrogen evolution. In situ measurements of hydrogen evolution and acetylene reduction by nodulated soybeans confirmed the results obtained with excised nodules. In an atmosphere of air, a major portion of the total electron flux available for the reduction of atmospheric nitrogen by either excised nodules or intact nodulated plants was utilized in the production of hydrogen gas. Some nonleguminous symbionts, such as Alnus rubra, and a few legumes (i.e., Vigns sinensis) apparently have evolved mechanisms of minimizing net hydrogen production, thus increasin their efficiency of electron. transfer to nitrogen. Our res ts indicate that the extent of hydrogen evolution during nitrogen reduction is a major factor affecting the efficiency of nitrogen fixation by many agronomically important legumes. The increasing world population and depletion of fossil fuel supplies have stimulated renewed interest in methods of increasing agricultural productivity while minimizing the consumption of fossil fuels. A major factor limiting agricultural production is nitrogen fertilizer, the synthesis of which consumes major quantities of energy. Approximately 3% (600 X 109 cubic feet; 16.8 X 109 meter3) of the natural gas consumed in the United States in 1973 was used for the synthesis of 17 X 106 U.S. tons (153 X 108 kg) of anhydrous ammonia (1, 2). About 10 X 106 U.S. tons of synthetic ammonia were used for nitrogen fertilizer to supply a portion of an annual agricultural nitrogen demand of about 18 X 106 U.S. tons (1, 2). A large part of the remaining need for nitrogen in agriculture was supplied by nitrogen-fixing organisms, such as legumes, which utilize photosynthetically stored solar energy to reduce atmospheric nitrogen to ammonia. Because the biological nitrogen-fixing process is not dependent upon nonrenewable energy resources, its use in agriculture should be maximized. Factors limiting biological nitrogen fixation therefore deserve thorough investigation (3,4).One characteristic of all cell-free nitrogenase preparations that might limit nitrogen fixation is the release of hydrogen gas concomitant with nitrogen reduction (5-11). During thi...

show abstract

“…N 2 reduction by Mo-and V-nitrogenases is strongly inhibited by carbon monoxide (CO) (5)(6)(7)(8)(9)(10). It is assumed that CO blocks electron flow in Mo-and V-nitrogenases at different stages, because hydrogen production by Mo-nitrogenase is largely unaffected by CO, whereas V-nitrogenase-catalyzed H 2 evolution decreases gradually with increasing CO concentrations (6).…”

mentioning

confidence: 99%

NifA- and CooA-Coordinated cowN Expression Sustains Nitrogen Fixation by Rhodobacter capsulatus in the Presence of Carbon Monoxide

et al. 2014

View full text Add to dashboard Cite

Rhodobacter capsulatus fixes atmospheric dinitrogen via two nitrogenases, Mo-and Fe-nitrogenase, which operate under different conditions. Here, we describe the functions in nitrogen fixation and regulation of the rcc00574 (cooA) and rcc00575 (cowN) genes, which are located upstream of the structural genes of Mo-nitrogenase, nifHDK. Disruption of cooA or cowN specifically impaired Mo-nitrogenase-dependent growth at carbon monoxide (CO) concentrations still tolerated by the wild type. The cooA gene was shown to belong to the Mo-nitrogenase regulon, which is exclusively expressed when ammonium is limiting. Its expression was activated by NifA1 and NifA2, the transcriptional activators of nifHDK. AnfA, the transcriptional activator of Fe-nitrogenase genes, repressed cooA, thereby counteracting NifA activation. CooA activated cowN expression in response to increasing CO concentrations. Base substitutions in the presumed CooA binding site located upstream of the cowN transcription start site abolished cowN expression, indicating that cowN regulation by CooA is direct. In conclusion, a transcription factor-based network controls cowN expression to protect Mo-nitrogenase (but not Fe-nitrogenase) under appropriate conditions.

show abstract

Inhibition of nitrogenase-catalyzed reductions

Cited by 181 publications

References 21 publications

Electron-paramagnetic-resonance studies on nitrogenase of Klebsiella pneumoniae. Evidence for acetylene- and ethylene-nitrogenase transient complexes

Electron-paramagnetic-resonance studies on nitrogenase of Klebsiella pneumoniae. Evidence for acetylene- and ethylene-nitrogenase transient complexes

Hydrogen evolution: A major factor affecting the efficiency of nitrogen fixation in nodulated symbionts

NifA- and CooA-Coordinated cowN Expression Sustains Nitrogen Fixation by Rhodobacter capsulatus in the Presence of Carbon Monoxide

Contact Info

Product

Resources

About