| 12916153 |
Semchyshyn HM, Dyl'ovyi MV, Lushchak VI: [pH-dependency of Escherichia coli catalase activity under modified culture conditions]. Ukr Biokhim Zh. 2002 Sep-Oct;74(5):34-41.
In the previous work we have found two peaks of catalase activity at acid and neutral pH in partially destroyed bacteria E. coli K12 KS400. The present study indicates that catalase activity with two pH-optimums is sensitive to pH of cultivation medium. The relative catalase activity of frozen-thawed bacteria preparations measured at pH 3.5 increased two-fold and activity measured at pH 7.0 didn't change by shift of medium pH from value 5.5 to 7.0. In analogical preparations of bacteria grown in slightly alkaline media activity with acid maximum was not observed, but activity with neutral maximum rose to 130% in comparison with the intact cells was revealed. Two peaks of activity differed in their sensitivity to bacteria destruction, heating, inhibition by NaN3 and AMT, oxidative stress. The analysis of recent literature information and experimental data leads us to conclude that the activity with neutral pH-optimum consists of two known catalase forms HPI and HPII in E. coli. The ratio of HPI and HPII is 70 and 30%, respectively what was concluded from inhibition of catalase activity with neutral pH-optimum by AMT. Properties of catalase activity with acid pH-optimum didn't corresponding to any known enzyme forms. It is suggested the activity measured at pH 3.5 is results of some unstable activator which acts in acid pH range. It is possible that the described activity with acid pH-optimum is specific for the used E. coli strain. Investigation of another strain of E. coli K12 AB1157 confirmed this idea where the activity peak with acid pH-optimum was not detected. |
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