[Effect of protonofore 2,4-dinitrophenol on catalase activity of intact Escherichia coli bacteria]

Catalase activity of intact E. coli bacteria had a broad pH-optimum (4.0-7.5). Addition of protonofore 2,4-dinitrophenol (200 microM) caused pH-dependency modification (6.5-7.0). Both the catalase activity and curves mode of native cells in the presence of dinitrophenol and cell-free extracts are almost identical. The loss of catalase activity at acid pH was caused by cells destruction and dinitrophenol addition, that makes it possible to suppose that this activity is connected with some membrane component functioning. The induction of "acid" catalase by oxidative stress was blocked with addition of chloramphenicol--protein synthesis inhibitor in prokaryotes. Probably this membrane complex is a part of OxyR regulon, because it is activated by hydrogen peroxide. The activation was not detected in the strain E. coli UM202, which is lacked of catalase HPI (H2O2 response). The catalase activity at acid pH was not observed in the strain E. coli AB1157, that produces both catalase forms and probably has the membrane defect. However, known genetic characteristics of AB1157 stain not let to identify a gene responsible for the "acid" catalase activity.