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KMID : 0545120030130020225
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Journal of Microbiology and Biotechnology
2003 Volume.13 No. 2 p.225 ~ p.229
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The Membrane-Bound NADH
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LEE, YOUNG JAE
CHO, KYEUNG HEE/KIM, YOUNG JAE
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Abstract
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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, QH_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 -NADH): ubiquinone-1 oxidoreductase was inhibited by about 33% with 60 ??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 ??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 (??Ψ) which was larger in the presence of Na^+ than that observed in the absence of Na^+. The ??Ψ was almost completely collapsed by 5 ??M carbonylcyanide m-chlorophenylhydrazone (CCCP), and approximately 50% inhibited by 100 ??M rotenone, or 60 ??M 2-heptyl-4- hydroxyquinoline (HQNO). Also, HQNO made the ?? Ψ 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.
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KEYWORD
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