The pentahaem enzyme cytochrome c nitrite reductase catalyses the reduction of nitrite to ammonia, a key reaction in the biological nitrogen cycle. The enzyme can also transform nitrogen monoxide and hydroxylamine, two potential bound reaction intermediates, into ammonia. Structural and mechanistic aspects of the multihaem enzyme are discussed in comparison with hydroxylamine oxidoreductase, a ...

Pathways of ammonia assimilation into glutamic acid were investigated in ammonia-grown and N2-fixing Clostridium kluyverii and Clostridium butyricum by measuring the specific activities of glutamate dehydrogenase, glutamine synthetase, and glutamate synthase. C. kluyverii had NADPH-glutamate dehydrogenase with a Km of 12.0 mM for NH4+. The glutamate dehydrogenase pathway played an important rol...

The utilization of nitrate and ammonia as nitrogen sources had different effects on the metabolism of glycolate in Cholorella sorokiniana. During photolithotrophic growth with nitrate as nitrogen source, glycolate was metabolized via the glycine-serine pathway. Ammonia, produced as a result of glycolate metabolism, was reassimilated by glutamine synthetase. Two isoforms of this enzyme were pres...

Electrochemical nitrogen-to-ammonia fixation is emerging as a sustainable strategy to tackle the hydrogen- and energy-intensive operations by Haber-Bosch process for ammonia production. However, current electrochemical nitrogen reduction reaction (NRR) progress is impeded by overwhelming competition from the hydrogen evolution reaction (HER) across all traditional NRR catalysts and the requirem...

Blood ammonia nitrogen was determined in 36 cases of hepatic coma and 63 cases of liver disease. Significant elevations (PL 0.001) were noted in coma due to hepatitis and cirrhosis and the mortality rate was 89% and 9 1.3% respectively. Raised ammonia nitrogen in hepatic coma is a sign of grave prognosis (JPMA 34 : 9, 1984).

Ammonia and urea are the primary forms of nitrogen excretion in teleost fish. There exists, however, a discrepancy between the sum of ammonia plus urea nitrogen and total nitrogen, indicating that 'unknown' nitrogen end products may play an important role in nitrogen metabolism. The current study analysed a wide range of nitrogen end products in both fed and fasted juvenile rainbow trout. Ammon...

Pathways of ammonia assimilation into glutamic acid in Bacillus azotofixans, a recently characterized nitrogen-fixing species of Bacillus, were investigated through observation by NMR spectroscopy of in vivo incorporation of 15N into glutamine and glutamic acid in the absence and presence of inhibitors of ammonia-assimilating enzymes, in combination with measurements of the specific activities ...

Deposition of nitrogen forms one of the largest threats to the vitality and biodiversity of Dutch nature areas. Of the two nitrogen compounds contributing to the total nitrogen deposition, Dutch sources of reduced nitrogen are estimated to contribute 47% to the total nitrogen deposition, whereas for oxidised nitrogen this is only 15%. For Dutch policy, it is therefore most effective to decrease...

The level of glutamine synthetase activity in Agmenellum quadruplicatum strain PR-6 was dependent on the nitrogen source used for growth and on the nutritional status of the cells. During exponential growth, glutamine synthetase activity was low in cells grown on ammonia, urea, or nitrate. During the transition from nitrogen replete to nitrogen starved growth, glutamine synthetase activity bega...

The acute toxicity of ammonia on Thulinius ruffoi (Bertolani, 1981), a eutardigrade isolated from a small waste water treatment plant (WWTP) in Poland, was estimated. Our results show that no active individuals survived a 24 h exposure to solutions equal to or higher than 125 mg/L of total ammonia nitrogen (NH3-N + NH4 (+)-N), which, under the conditions in our experiment, was equivalent to 1.1...