1998 Fiscal Year Final Research Report Summary
Molecular Evolution of Denitrifying Systems of Fungi and Actinomycetes
| Project/Area Number |
08406008
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
応用微生物学・応用生物化学
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| Research Institution | University of Tsukuba |
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Principal Investigator |
SHOUN Hirofumi Institute of Applied Biochemistry, University of Tsukuba, Professor, 応用生物化学系, 教授 (70012036)
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| Co-Investigator(Kenkyū-buntansha) |
TAKAYA Naoki Institute of Applied Biochemistry, University of Tsukuba, Research Associate, 応用生物化学系, 助手 (50282322)
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| Project Period (FY) |
1996 – 1998
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| Keywords | denitrification / Fusarium oxysporum / mitochondria / actinomycetes / cytochrome P450nor / nitric oxide reductase / nitrate reductase / nitrite reductase |
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| Research Abstract |
(1) The denitrifying systems of the fungus Fusarium oxysporum and Cylindrocarpon tonkinense were shown to be localized at the mitochondrion and denitrifying enzyme activities such as nitrate reductase and nitrite reductase activities were detected in the denitrifying mitochondria coupling to the synthesis of ATP.The results resulted in the finding of an anaerobic respiration system in the fungal mitochondrion. We observed the mitochondria in the fungal cells grown under denitrifying conditions also by electron microscopy as well as the immuno-fluorescent staining, and found that the fungal mitochondria are normally progressed even under such oxygen-restricted conditions and denitrifying systems are localized to the mitochondria.
(2) Cytochrome P45Onor catalyzes a unique reaction as P450 although it belongs to the P450 superfamily. We succeeded in determining the crystal structure of P450nor, which afforded a great advance in clarifying its reaction mechanism.
(3) Although we found denitr
… More
ifying activities in fungi, such activities had not been found in important microbial taxa, yeasts and actinomycetes. So we screened the activities among those microorganisms and found many denitrifiers in yeasts and actinomycetes. We clarified the denitrifying systems of the actinomycete Streptomyces thioluteus and the yeasts Trichosporon cutaneum and Fellomyces fuzhouensis, We found the occurrence of P450nor in T.cutaneum and purified nitrite reductase (Nir) and azurin from S.thioluteus.
(4) We isolated and charactgerized components of the denitrifying systems of fungi that were not isolated so far, such as nitrate reductase (Nar), flavohemoglobin, and cytochrome c_<549> from F.oxysporum and Nir from C.tonkinense.
These results demonstrated for the first time the occurrence of denitrifying activities among fungi, yeasts, and actinomycetes. The eukaryotic denitrifying systems were shown to be localized at the mitochondrion coupling to the synthesis of ATP and thus act as an anaerobic respiration. These results presented not only the existence of a novel respiration system in the mitochondrion but also important aspects and subjects to be elucidated concerning the evolution of the respiratory systems Less
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