A NOVEL AEROBIC RESPIRATORY CHAIN-LINKED NADH OXIDASE SYSTEM IN ZYMOMONAS-MOBILIS

Membrane vesicles prepared from Zymomonas mobilis oxidized NADH exclus ively, whereas deamino-NADH was little oxidized. In addition, the resp iratory chain-linked NADH oxidase system exhibited only a single appar ent K-m value of approximately 66 mu M for NADH. The NADH oxidase was highly sensitive to the respiratory chain inhibitor 2-heptyl-4-hydroxy quinoline-N-oxide. However, the NADH:quinone oxidoreductase was not se nsitive to 2-heptyl-4-hydroxyquinoline-N-oxide and was highly resistan t to another respiratory chain inhibitor, rotenone. Electron transfer from NADH to oxygen generated a proton electrochemical gradient (insid e positive) in inside-out membrane vesicles. In contrast, electron tra nsfer from NADH to ubiquinone-l generated no electrochemical gradient. These findings indicate that Z. mobilis possesses only NADH:quinone o xidoreductase lacking the energy coupling site.