Regulation of catalase level in Escherichia coli K12

The synthesis of catalase (H 2 O 2 :H 2 O 2 oxidoreductase, EC 1.11.1.6) in Escherichia coli K 12 was regulated by repression–induction and catabolite repression. Transient repression by glucose was also demonstrated. Under certain conditions, preferential synthesis was observed. Enzyme synthesis was induced in glycerol-grown cells by 0.15 to 0.2 μmol H 2 O 2 (5–6 μg) per millilitre of culture, added at 10 to 15-min intervals, which were shortened progressively as the level of catalase in the cells rose. Catabolite repression of catalase synthesis was demonstrated with glucose, glycerol, maltose, lactose, xylose, mannitol, sorbitol, and trehalose, and to a lesser extent with arabinose, galactose, sucrose, rhamnose, and dulcitol as sole carbon sources in mineral medium. Catabolite repression was prevented by anaerobic growth and nitrogen starvation. All TCA-cycle intermediates examined afforded high catalase levels when serving as sole carbon sources. High catalase levels were also obtained when cells were grown on nutrient broth, nutrient agar, casitone, and peptone.