title: Nitrogen assimilation in Rhodopseudomonas acidophila.
abstract: Rhodopseudomonas acidophila strain 7050 assimilated ammonia via a constitutive glutamine synthetase/glutamate synthase enzyme system. Glutamine synthetase had a Km for NH+4 of 0.38 mM whilst the nicotinamide adenine dinucleotide linked glutamate synthase had a Km for glutamine of 0.55 mM. R. acidophila utilized only a limited range of amino acids as sole nitrogen sources: L-alanine, glutamine and asparagine. The bacterium did not grow on glutamate as sole nitrogen source and lacked glutamate dehydrogenase. When R. acidophila was grown on L-alanine as the sole nitrogen source in the absence of N2 low levels of a nicotinamide adenine dinucleotide linked L-alanine dehydrogenase were produced. It is concluded, therefore, that this reaction was not a significant route of ammonia assimilation in this bacterium except when glutamine synthetase was inhibited by methionine sulphoximine. In L-alanine grown cells the presence of an active alanine-glyoxylate aminotransferase and, on occasions, low levels of an alanine-oxaloacetate aminotransferase were detected. Alanine-2-oxo-glutarate aminotransferase could not be demonstrated in this bacterium.
mesh_terms: D000409:Alanine / Q000378:metabolism; D000410:Alanine Transaminase / Q000378:metabolism; D000594:Amino Acid Oxidoreductases / Q000378:metabolism; D001216:Asparagine / Q000378:metabolism; D002474:Cell-Free System; D005969:Glutamate Dehydrogenase / Q000378:metabolism; D005970:Glutamate Synthase / Q000378:metabolism; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D005971:Glutamates / Q000378:metabolism; D005973:Glutamine / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D012241:Rhodopseudomonas / Q000378:metabolism*
chemical_list: D005971:Glutamates; D005973:Glutamine; D001216:Asparagine; D000594:Amino Acid Oxidoreductases; D005970:Glutamate Synthase; D005969:Glutamate Dehydrogenase; D000410:Alanine Transaminase; D005974:Glutamate-Ammonia Ligase; D009584:Nitrogen; D000409:Alanine