Regulation of Escherichia coli catalases by anaerobiosis and catabolite repression

Escherichia coli has two forms of catalases, HPI and HPII. Both enzymes, but mainly HPII, are induced in cells reaching the stationary growth phase or under anaerobic conditions and are repressed in the presence of glucose. The induction at the stationary phase is dependent on fnr, a gene that regulates the expression of anaerobically induced proteins. The inhibition by glucose is not affected by cyclic AMP (cAMP) but is reduced in a crp mutant. The results show that HPII belongs to the group of genes controlled by the Fnr protein and is catabolically repressed in a manner that is independent of cAMP.