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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The mechanism of ammonia assimilation in Methanosarcina barkeri and Methanobacterium thermoautotrophicum was documented by analysis of enzyme activities, 13NH3 incorporation studies, and comparison of growth and enzyme activity levels in continuous culture. Glutamate accounted for 65 and 52% of the total amino acids in the soluble pools of M. barkeri and M. thermoautotrophicum. Both organisms contained significant activities of glutamine synthetase, glutamate synthase, glutamate oxaloacetate transaminase, and glutamate pyruvate transaminase. Hydrogen-reduced deazaflavin-factor 420 or flavin mononucleotide but not NAD, NADP, or ferredoxin was used as the electron donor for glutamate synthase in M. barkeri. Glutamate dehydrogenase activity was not detected in either organism, but alanine dehydrogenase activity was present in M. thermoautotrophicum. The in vivo activity of the glutamine synthetase was verified in M. thermoautotrophicum by analysis of 13NH3 incorporation into glutamine, glutamate, and alanine. Alanine dehydrogenase and glutamine synthetase activity varied in response to [NH4+] when M. thermoautotrophicum was cultured in a chemostat with cysteine as the sulfur source. Alanine dehydrogenase activity and growth yield (grams of cells/mole of methane) were highest when the organism was cultured with excess ammonia, whereas growth yield was lower and glutamine synthetase was maximal when ammonia was limiting.
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PMID:Ammonia assimilation and synthesis of alanine, aspartate, and glutamate in Methanosarcina barkeri and Methanobacterium thermoautotrophicum. 612 78

Illuminated pea (Pisum sativum) chloroplasts actively catalyzed (glutamine plus alpha-ketoglutarate)-dependent O(2) evolution (average of 12 preparations 10.6 mumole mg chlorophyll per hour). The reaction was specific for glutamine and alpha-ketoglutarate; concentrations of 0.2 mm alpha-ketoglutarate and 0.6 mm glutamine, respectively, effected half-maximum rates of O(2) evolution. The reaction was inhibited by 3-(3,4-dichlorophenyl)-1-1-dimethylurea and did not occur in the dark. After osmotic shock chloroplasts did not catalyze O(2) evolution. The reaction was inhibited by azaserine and glutamate but not by 10 mm ammonia, 2.5 mm methionine sulfoximine, or 5 mm amino-oxyacetate; addition of amino-oxyacetate together with aspartate inhibited O(2) evolution. Arsenate (3 mm) enhanced O(2) evolution. The highest molar ratio for O(2) evolved per mole of alpha-ketoglutarate supplied was 0.40; the corresponding values for glutamine in the absence and presence of 3 mm arsenate were 0.20 and 0.24, respectively. The (glutamine plus alpha-ketoglutarate)-dependent O(2) evolution is attributed to photosynthetically coupled glutamate synthase activity and the activity is sufficient to account for the assimilation of inorganic nitrogen. The low molar ratio for glutamine is discussed.Chloroplasts also catalyzed (aspartate plus alpha-ketoglutarate)-dependent O(2) evolution but this reaction was inhibited by 5 mm amino-oxyacetate and it was insensitive to azaserine and methionine sulfoximine. This reaction was attributed to transaminase and photosynthetically coupled malate dehydrogenase activities.
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PMID:A polarographic study of glutamate synthase activity in isolated chloroplasts. 1666 92