title: Regulation of Glutamine Transport in Escherichia coli.
abstract: The formation of the high-affinity (Km equal to 0.2 muM) L-glutamine transport system of Escherichia coli strain 7 (Lin) appears to be subject to the same major control as the glutamine synthetase (EC 6.3.1.2) of this gram-negative organism. Culture of cells under nitrogen-limited conditions provides maximum derepression of both the glutamine synthetase and the glutamine transport system. Nutritional conditions providing a rich supply of ammonium salts or available sources of nitrogen, i.e., conditions which repress the formation of glutamine synthetase, provide three- and 20-fold repression, respectively, of the glutamine transport system. Culture of cells with glutamine supplements of 2 mM does not increase the repression of high-affinity glutamine transport system beyond the level observed in the absence of glutamine. A second kinetically distinct low-affinity component of glutamine. A second kinetically distinct low-affinity component of glutamine uptake is observed in cells cultured with a glutamine-depleted nutrient broth. This second component is associated with the appearance of glutaminase A (EC 3.5.1.2) and asparaginase I (EC 3.5.1.1), a periplasmic enzyme. Parallel changes were observed in the levels of the high-affinity glutamine transport system and the glutamine synthetase when cells were cultured with the carbon sources: glucose, glycerol, or succinate.
mesh_terms: D000641:Ammonia / Q000378:metabolism; D001215:Asparaginase / Q000378:metabolism; D001693:Biological Transport, Active; D002474:Cell-Free System; D004794:Enzyme Repression; D004926:Escherichia coli / Q000201:enzymology / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D005969:Glutamate Dehydrogenase / Q000378:metabolism; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D005972:Glutaminase / Q000378:metabolism; D005973:Glutamine / Q000378:metabolism*; D005990:Glycerol / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D012492:Salts; D013237:Stereoisomerism; D013386:Succinates / Q000378:metabolism
chemical_list: D000644:Quaternary Ammonium Compounds; D012492:Salts; D013386:Succinates; D005973:Glutamine; D000641:Ammonia; D005969:Glutamate Dehydrogenase; D001215:Asparaginase; D005972:Glutaminase; D005974:Glutamate-Ammonia Ligase; D005947:Glucose; D005990:Glycerol