Oxygen consumption of lactobacilli. II. relationship between NADH oxidase activity and oxygen consumption of Lactobacillus acidophilus (author's transl)

Abstract

Relationship between activities of oxidases and oxygen consumption in Lactobacillus acidophilus was examined. NADH oxidase activity (about 600 nmol/min/mg protein) was found in the extract of the cells grown in a medium containing glucose. This enzyme was cytochrome-independent and mainly found in the supernatant fluid obtained from homogenized cells by centrifugation at 105000×g. Its optimum pH was at 5.9 and its Km value for NADH was 2.04×10-5M. Both enzyme activity and oxygen consumption increased to the maximum at late logarithmic phase and rapidly decreased at the stationary phase. Oxygen consumption of the cells grown in a medium containing polyols was 2-4 times higher than that of the cells grown in a medium containing hexoses, and NADH oxidase activity of the former was also 2-4 times higher than that of the latter. Variation in the activity of NADH oxidase was roughly proportional to that of oxygen consumption. Oxygen consumption of the cells in the presence of pyruvate or lactate was also observed to be KCN-insensitive. Under these conditions, effect of carbon source used in the culture medium on oxygen consumption of the cells was similar to that in the presence of glucose. These results suggest that NADH oxidase is related to the oxygen consumption of L. acidophilus.