title: Ammonia-sensitive mutant of Klebsiella aerogenes.
abstract: We have isolated a temperature-sensitive mutant of Klebsiella aerogenes unable to grow aerobically at 42 C in standard glucose minimal medium containing 0.03 M ammonium sulfate as a source of nitrogen. This strain, MK810, will grow at this temperature in significantly lower concentrations of ammonia (1 mM) or when ammonia is replaced by a growth rate-limiting source of nitrogen such as histidine or glutamate. A detailed physiological characterization and preliminary biochemical tests support the contention that the mutant has an altered alpha-ketoglutarate dehydrogenase that at the restrictive condition fails to manufacture sufficient succinyl-coenzyme A. We explain the ammonia sensitivity by the dual role of alpha-ketoglutarate as substrate for the formation of succinyl-coenzyme A and glutamate. A defect in the enzyme necessary for the production of succinyl-coenzyme A makes ammonia an overly effective competitor for alpha-ketoglutarate.
mesh_terms: D000332:Aerobiosis; D000641:Ammonia / Q000378:metabolism*; D003065:Coenzyme A / Q000096:biosynthesis; D005947:Glucose / Q000378:metabolism; D005971:Glutamates / Q000378:metabolism; D006639:Histidine / Q000378:metabolism; D007655:Ketoglutarate Dehydrogenase Complex / Q000378:metabolism; D007656:Ketoglutaric Acids / Q000378:metabolism; D007709:Klebsiella / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D009154:Mutation; D013696:Temperature
chemical_list: D005971:Glutamates; D007656:Ketoglutaric Acids; D006639:Histidine; D000641:Ammonia; D007655:Ketoglutarate Dehydrogenase Complex; D005947:Glucose; D003065:Coenzyme A