• Journal of Microbiology and Biotechnology
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• 제13권2호
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• pp.225-229
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• 2003

Each oxidoreductase activity of the aerobic respiratory chain-linked NADH oxidase system in the marine bacterium Pseudomonas nautica was stimulated by monovalent cations including $Na^+,\;Li^+,\;and\;K^+$. In the presence of NADH or deamino-NADH as electron donors, $GH_2$ formation was approximately 1.3-fold higher in the presense of 0.08 M of $Na^+\;than\;K^+$, Whereas the other reductase activities were not significantly higher in $Na^+\;than\;K^+$. The optimal pH of NADH (or deamino-NADH):ubiquinone-1 oxidoreductase was 9.0 in the presence of 0.08 M NaCl. The activity of NADH (or deamino-NADH):ubiquinone-1 oxidoreductase was inhibited by about 33% with $60{\mu}M$ 2-heptyl-4-hydroxyquinoline-N-oxide (HQNO). The activity of NADH (deamino-NADH): ubiquinone-1 oxidoreductase was inhibited by about 32 to 38% with $80{\mu}M$ rotenone, whereas the activity was highly resistant to capsaicin. On the other hand, electron transfer from NADH or deamino-NADH to ubiquinone-1 generated a membrane potential (${\Delta}{\psi}$) which was larger in the presence of $Na^+$ than that observed in the absence of $Na^+$. The ${\Delta}{\psi}$ was almost completely collapsed by $5{\mu}M$ carbonylcyanide m-chlorophenylhydrazone(CCCP), and approximately 50% inhibited by $100{\mu}M$ rotenone, or $60{\mu}M$ 2-heptyl-4-hydroxyquinoline (HQNO). Also, HQNO made the ${\Delta}{\psi}$ very unstable. The results suggest that the enzymatic and energetic properties of the NADH:ubiquinone oxidoreductase of P. nautica are quite different, compared with those of other marine halophilic bacteria.

• 한국생명과학회:학술대회논문집
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• 한국생명과학회 2003년도 제40회 국제학술심포지움
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• pp.131-131
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• 2003

• Journal of Microbiology and Biotechnology
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• 제15권5호
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• pp.1080-1086
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• 2005

Membranes prepared from Vibrio natriegens oxidized both NADH and deamino-NADH as substrates. The maximum activity of the membrane-bound NADH oxidase was obtained at about pH 8.5 in the presence of 0.2 M NaCl, whereas that of the NADH:ubiquinone oxidoreductase was obtained at about pH 7.5 in the presence of 0.2 M NaCl. Electron transfer from NADH or deamino-NADH to ubiquinone-l or oxygen generated a considerable membrane potential (${\Delta}{\psi}$), which occurred even in the presence of $20{\mu}M$ carbonylcyanide m-chlorophenylhydrazone (CCCP). However, the ${\Delta}{\psi}$ was completely collapsed by the combined addition of $10{\mu}M$ CCCP and $20{\mu}M$ monensin. On the other hand, the activity of the NADH oxidase and the ${\Delta}{\psi}$ generated by the NADH oxidase system were inhibited by about $90\%$ with $10{\mu}M$ HQNO, whereas the activity of the NADH:ubiquinone oxidoreductase and the ${\Delta}{\psi}$ generated at the NADH:ubiquinone oxidoreductase segment were inhibited by about $60\%$. Interestingly, the activity of the NADH:ubiquinone oxidoreductase and the ${\Delta}{\psi}$ generated at the NADH:ubiquinone oxidoreductase segment were resistant to the respiratory chain inhibitors such as rotenone, capsaicin, and $AgNO_3$, and the activity of the NADH oxidase and the ${\Delta}{\psi}$ generated by the NADH oxidase system were very sensitive only to $AgNO_3$. It was concluded, therefore, that V. natriegens cells possess a $AgNO_3$-resistant respiratory $Na^+$ pump that is different from the $AgNO_3$-sensitive respiratory $Na^+$ pump of a marine bacterium, Vibrio alginolyticus.