Purification and Characterization of Sporolactobacillus inulinus NADH Oxidase and Its Physiological Role in Aerobic Metabolism of the Bacterium

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NADH oxidase was purified to homogeneity from aerobic cells of Sporolactobacillus inulinus. The N-terminal amino acid sequence showed high similarity to those of the NADH oxidase from Amphibacillus xylanus and the H_2O_2-forming NADH oxidase from Steptococcus mutans. S. inulinus NADH oxidase is a homodimer composed of subunits and with a molecular mass of 53 kDa. It catalyzes the reduction of oxygen to hydrogen peroxide, and, in the presence of a low molecular weight disulfide-containing component (AhpC) from A. xylanus, of hydrogen peroxide to water. The V_<max> values for hydrogen peroxide and cumene hydroperoxide reduction were 9,300 and 8,300 min^<-1>, respectiely at 25℃. These values are similar to the V_<max> values for hydrogen peroxide and cumene hydroperoxide reduction with the NADH oxidase from A. xylanus. Cell extracts from S. inulinus cultures grown under anaerobic and aerobic cnditions reacted with antibodies against the AhpC protein from A. xylanus. An immunoreactige AhpC-like 21 kDa proteinw as induced in S. inulinus under aerobic, but not under anaerobic conditions. The results suggest that AhpC is involved in the aerobic metabolism of S. inulinus, which lacks a respiratory chain and catalase. The AhpC-NADH oxidase system is thougth to function as a scavenging system for hydrogen peroxide formed aerobically.
社団法人日本生物工学会の論文
1997-07-25