title: Observations on enzymes of ammonia assimilation in two different strains of Cyanidium caldarium.
abstract: Two strains of Cyanidium caldarium, one able to utilize nitrate as a substrate, and the other not, were tested for the presence of enzymes of ammonia assimilation. The nitrate-assimilating strain exhibits glutamate dehydrogenase activity. By contrast, the other strain lacks glutamate dehydrogenase; it possesses high alanine dehydrogenase and L-alanine aminotransferase activities which suggest that this strain may incorporate ammonia through reductive amination of pyruvate and may form glutamate from 2-ketoglutarate by a transamination reaction with alanine. Neither strain reveals glutamate synthase activity. Both strains contain similar levels of glutamine synthetase.
mesh_terms: D000409:Alanine; D000410:Alanine Transaminase / Q000378:metabolism; D000594:Amino Acid Oxidoreductases / Q000378:metabolism; D000641:Ammonia / Q000378:metabolism*; D056890:Eukaryota / Q000201:enzymology*; D005969:Glutamate Dehydrogenase / Q000378:metabolism; D005970:Glutamate Synthase / Q000378:metabolism; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism; D010802:Phylogeny
chemical_list: D009566:Nitrates; D000641:Ammonia; D000594:Amino Acid Oxidoreductases; D005970:Glutamate Synthase; D005969:Glutamate Dehydrogenase; D000410:Alanine Transaminase; D005974:Glutamate-Ammonia Ligase; D000409:Alanine