Amino acids as repressors of nitrogenase biosynthesis in Klebsiella pneumoniae.
Nitrogenase biosynthesis in Klebsiella pneumoniae including mutant strains, which produce nitrogenase in the presence of NH+4 (Shanmugam, K.T., Chan, Irene, and Morandi, C. (1975) Biochim. Biophys. Acta 408, 101--111) is repressed by a mixture of L-amino acids. Biochemical analysis shows that glutamine synthetase activity in strains SK-24, SK-28, and SK-29 is also repressed by amino acids, with no detectable effect on glutamate dehydrogenase. Among the various amino acids, L-glutamine in combination with L-aspartate was found to repress nitrogenase biosynthesis completely. In the presence of high concentrations of glutamine (1 mg/ml) even NH+4 repressed nitrogenase biosynthesis in the strains SK-27, SK-37, SK-55 and SK-56. Under these conditions, increased glutamate dehydrogenase activity was also detected. Physiological studies show that nitrogenase derepressed strains are unable to utilize NH+4 as sole source of nitrogen for biosynthesis of glutamate for biosynthesis of glutamate, whereas back mutations leading to NH+4 utilization results in sensitivity to repression by NH+4. These findings suggest that amino acids play an important role as regulators of nitrogen fixation.
D000596:Amino Acids / Q000494:pharmacology*; D001224:Aspartic Acid / Q000494:pharmacology; D004794:Enzyme Repression / Q000187:drug effects; D005969:Glutamate Dehydrogenase / Q000378:metabolism; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D005973:Glutamine / Q000494:pharmacology; D007711:Klebsiella pneumoniae / Q000187:drug effects / Q000201:enzymology*; D008954:Models, Biological; D009154:Mutation; D009591:Nitrogenase / Q000096:biosynthesis* / Q000378:metabolism; D013045:Species Specificity
D000596:Amino Acids; D005973:Glutamine; D001224:Aspartic Acid; D009591:Nitrogenase; D005969:Glutamate Dehydrogenase; D005974:Glutamate-Ammonia Ligase