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Differential roles of the Escherichia coli fumarases and fnr-dependent expression of fumarase B and aspartase

Sally A. Woods, John R. Guest
DOI: http://dx.doi.org/10.1111/j.1574-6968.1987.tb02545.x 219-224 First published online: 1 December 1987


The physiological functions of the Escherichia coli fumarases A, B, and C (FUMA, B and C) were investigated using strains containing multicopy plasmids expressing each of the fum genes, and with single-copy fum-lacZ fusions. The results showed that FUMA is the critic acid cycle enzyme because it was strongly expressed under aerobic conditions but repressed by glucose and anaerobiosis. FUMB and FUMC were less susceptible to repression by glucose and anaerobiosis, and FUMB was identified as an anaerobic enzyme because its anaerobic expression was controlled by the anaerobic transcriptional activator, FNR. The expression of an aspA-lacZ fusion was also shown to be fnr-dependent.

Key words
  • Fumarase
  • Aspartase
  • fnr gene
  • fum gene
  • aspA gene
  • Citric acid cycle
  • Anaerobic metabolism
  • Escherichia coli

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