Neubauer H, Götz F
Mikrobielle Genetik, Universität Tübingen, Tübingen, Germany.
J Bacteriol. 1996 Apr;178(7):2005-9. doi: 10.1128/jb.178.7.2005-2009.1996.
Staphylococcus carnosus reduces nitrate to ammonia in two steps. (i) Nitrate was taken up and reduced to nitrite, and nitrite was subsequently excreted. (ii) After depletion of nitrate, the accumulated nitrite was imported and reduced to ammonia, which again accumulated in the medium. The localization, energy gain, and induction of the nitrate and nitrite reductases in S. carnosus were characterized. Nitrate reductase seems to be a membrane-bound enzyme involved in respiratory energy conservation, whereas nitrite reductase seems to be a cytosolic enzyme involved in NADH reoxidation. Syntheses of both enzymes are inhibited by oxygen and induced to greater or lesser degrees by nitrate or nitrite, respectively. In whole cells, nitrite reduction is inhibited by nitrate and also by high concentrations of nitrite (> or = 10 mM). Nitrite did not influence nitrate reduction. Two possible mechanisms for the inhibition of nitrite reduction by nitrate that are not mutually exclusive are discussed. (i) Competition for NADH nitrate reductase is expected to oxidize the bulk of the NADH because of its higher specific activity. (ii) The high rate of nitrate reduction could lead to an internal accumulation of nitrite, possibly the result of a less efficient nitrite reduction or export. So far, we have no evidence for the presence of other dissimilatory or assimilatory nitrate or nitrite reductases in S. carnosus.
肉葡萄球菌将硝酸盐分两步还原为氨。（i）硝酸盐被吸收并还原为亚硝酸盐，随后亚硝酸盐被排出。（ii）硝酸盐耗尽后，积累的亚硝酸盐被导入并还原为氨，氨再次在培养基中积累。对肉葡萄球菌中硝酸盐和亚硝酸盐还原酶的定位、能量获取及诱导情况进行了表征。硝酸盐还原酶似乎是一种参与呼吸能量保存的膜结合酶，而亚硝酸盐还原酶似乎是一种参与NADH再氧化的胞质酶。两种酶的合成均受氧气抑制，分别被硝酸盐或亚硝酸盐不同程度地诱导。在完整细胞中，亚硝酸盐还原受硝酸盐以及高浓度亚硝酸盐（≥10 mM）抑制。亚硝酸盐不影响硝酸盐还原。讨论了硝酸盐抑制亚硝酸盐还原的两种并非相互排斥的可能机制。（i）由于硝酸盐还原酶比活性较高，预计它会氧化大部分NADH。（ii）硝酸盐的高还原速率可能导致亚硝酸盐在细胞内积累，这可能是亚硝酸盐还原或输出效率较低的结果。到目前为止，我们没有证据表明肉葡萄球菌中存在其他异化或同化硝酸盐或亚硝酸盐还原酶。
