PMID: 8101Jul 21, 1976

Amino acids as repressors of nitrogenase biosynthesis in Klebsiella pneumoniae

Biochimica Et Biophysica Acta
K T Shanmugam, C Morandi


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.


Jan 1, 1982·Molecular & General Genetics : MGG·D RiesenbergC Kari
Jan 1, 1979·Archives of Microbiology·H Hennecke, K T Shanmugam
Dec 27, 2002·The Journal of General and Applied Microbiology·Raman Rai, Gabriele Rieder

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