Characteristics of nitrite reductase activity in Lactobacillus lactis TS4

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Abstract
Nitrite reductase activity in Lactobacillus lactis TS4 was induced by the presence of nitrite and was active under anaerobic conditions. An electron donor was required. Glucose was the most efficient donor in whole cells, while NADH was the most efficient in cell extracts. The optimum nitrite concentration for reduction was 2.0 mM, with higher levels sharply inhibiting activity. The pH optimum for nitrite reduction by resting cell suspensions was 7.2, and the temperature optimum was 30 °C. High levels of NADH oxidase activity in cell extracts interfered with nitrite reductase activity. Fractionation of the cell extract by ultracentrifugation and ammonium sulphate precipitation decreased the specific activity of NADH oxidase by 40 and 41%, respectively. Nitrite reductase activity was detected in the supernatant fluid after centrifugation of cell extract at 226 000 × g for 1 h.