| | 1 | Author
| Kassem Alef | Requires cookie* | | | Title
| in Rhodopseudomonas capsulata AD 2  | | | | Abstract
| Nitrate assimilation by Rhodopseudomonas capsulata A D 2 was com pletely inhibited by ammonium only in young well illuminated cultures. At higher densities (A660 about 0.5) the addition o f ammonium had no inhibitory effect, but the nitrate was only reduced to the level o f nitrite, which appeared in the medium. Under both conditions the cellular level o f nitrate reductase activity remained unaffected. In marked contrast to other R. capsulata strains both ammonium sensitive and insensitive cells could reduce nitrate in the light and in the darkness. In the light up to 90% of the reduced nitrate was assim ilated, but in the dark the reduced nitrate was stoichiometrically excreted as nitrite. This behaviour was only shown by R. capsulata A D 2 and BK5, while in other strains the nitrate assim ilation was always com pletely inhibited by ammonium. The role o f photosynthesis and respiration by the regulation o f nitrate reduction is discussed. | | | |
Reference
| Z. Naturforsch. 39c, 85—8 (1984); received Novem ber 10 1983 | | | |
Published
| 1984 | | | |
Keywords
| Nitrate Reduction, Regulation, Rhodopseudomonas capsulata | | | |
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| default:Reihe_C/39/ZNC-1984-39c-0085.pdf | | | | Identifier
| ZNC-1984-39c-0085 | | | | Volume
| 39 | |
| 2 | Author
| Susanne Bickel-Sandkötter, Martina Ufer | Requires cookie* | | | Title
| Properties of a Dissimilatory Nitrate Reductase from the Halophilic Archaeon Haloferax volcanii | | | | Abstract
| Grown under anaerobic conditions in presence of nitrate, Haloferax volcanii shows nitrate reduction and accumulation of nitrite in the culture medium. We found a membrane-asso-ciated nitrate reductase, which could easily be solubilized by gently stirring of isolated mem branes. Surprisingly, this nitrate reductase requires no NaCl for its activity. A medium pH of 7.5 and high temperatures up to 80 °C are necessary for optimum activity. Kinetic studies showed that the apparent K M was 0.36 mmol/1 for nitrate and 80 ^mol/1 for dithionite-reduced methyl viologen. The respiratory chain inhibitor cyanide effects nitrate reduction noncompe-titively with respect to nitrate with a K \ of 0.3 mmol/1. Azide was a strong inhibitor: The concentration required for half maximal inhibition was 60 |amol/l, whereas thiocyanate and chlorate were much weaker inhibitors. The isolated enzyme was partially purified by frac tionated precipitation using polyethylene glycol. SDS gel electrophoresis resulted in three putative subunits of the nitrate reductase of molecular masses of about 100, 61, and 31 kDa. | | | |
Reference
| Z. Naturforsch. 50c, 365—372 (1995); received February 6/February 27 1995 | | | |
Published
| 1995 | | | |
Keywords
| Archaeon, Haloferax volcanii, Dissimilatory Nitrate Reductase, Nitrate Reduction, Inhibition | | | |
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| default:Reihe_C/50/ZNC-1995-50c-0365.pdf | | | | Identifier
| ZNC-1995-50c-0365 | | | | Volume
| 50 | |
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