Enzyme localization and orientation of the active site of dissimilatory nitrite reductase from Bacillus firmus |
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Authors: | Katsuro Urata Toshio Satoh |
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Institution: | (1) Oyama National College of Technology, Nakakuki 771, 323 Oyama, Tochigi, Japan;(2) Botanical Institute, Faculty of Science, Hiroshima University, Higashi-senda-machi 1-1-89, 730 Hiroshima, Japan |
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Abstract: | The location of the dissimilatory nitrite reductase and orientation of its reducing site of the Grampositive denitrifier, Bacillus firmus NIAS 237 were examined. Approximately 90% of the total dissimilatory nitrite reductase activity with ascorbate-reduced phenazine methosulfate (PMS) as the electron donor was on the protoplast membrane. Nitrite induced with intact Bacillus cells an alkalinization in the external medium, followed by acidification. The electron transfer inhibitor, 2-heptyl-4-hydroxyquinoline-N-oxide, which blocked nitrite reduction with endogenous substrates, inhibited the acidification, but not the alkalinization. Alkalinization was not affected with ascorbate-reduced PMS as the artificial electron donor. This indicated that the alkalinization is not associated with proton consumption outside the cytoplasmic membrane by the extracellular nitrite reduction. The dissimilatory nitrite reductase of B. firmus NIAS 237 was located on the cytoplasmic membrane, and its reducing site is suggested to be on the inner side of this membrane.Abbreviations CCCP
carbonylcyanide m-chlorophenylhydrazone
- HOQNO
2-heptyl-4-hydroxyquinoline-N-oxide
- PMS
phenazine methosulfate
- H+/NO
inf2
sup-
ratio
number of consumed protons in the external medium per one ion of NO
inf2
sup-
reduced |
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Keywords: | Gram-positive denitrifier Bacillus firmus Dissimilatory nitrite reductase Subcellular localization |
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