title: Denitrification of nitrate by the fungus Cylindrocarpon tonkinense.
abstract: The denitrifying fungus Cylindrocarpon tonkinense was thought to be able to denitrify only nitrite (NO2-) but not nitrate (NO3-) to form nitrous oxide (N2O). Here we found, however, that C. tonkinense can denitrify NO3- under certain conditions. Presence of ammonium (NH3+) in addition to NO3- and the use of a fermentable sugar as an electron donor were key conditions for inducing the denitrifying activity. Such induction accompanied a remarkable increase in the intracellular level of the enzyme activities related to NO3- metabolism. These activities contained assimilatory type NADPH (or NADH)-dependent NO3- reductase (aNar), dissimilatory nitrite reductase (dNir), and nitric oxide reductase (P450nor), but did not contain ubiquinol-dependent, dissimilatory NO3- reductase (dNar). The denitrification was inhibited by tungstate, an inhibitor of Nar. These results demonstrated occurrence of a novel type of denitrification in C. tonkinense, in which assimilatory type Nar is possibly involved.
authors.affiliation: Institute of Applied Biochemistry, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan.
authors.forename: Tomo-o
authors.initials: TO
authors.lastname: Watsuji
authors.forename: Naoki
authors.initials: N
authors.lastname: Takaya
authors.forename: Akira
authors.initials: A
authors.lastname: Nakamura
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Shoun
mesh_terms: D000641:Ammonia / Q000494:pharmacology; D001203:Ascomycota / Q000378:metabolism*; D002474:Cell-Free System; D003470:Culture Media; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004791:Enzyme Inhibitors; D009249:NADP / Q000378:metabolism; D009565:Nitrate Reductases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism*; D009572:Nitrite Reductases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism; D010088:Oxidoreductases / Q000037:antagonists & inhibitors / Q000378:metabolism; D017973:Tungsten Compounds / Q000494:pharmacology
chemical_list: D003470:Culture Media; D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; D009566:Nitrates; D009573:Nitrites; D017973:Tungsten Compounds; D009249:NADP; D000641:Ammonia; D003577:Cytochrome P-450 Enzyme System; D010088:Oxidoreductases; D009565:Nitrate Reductases; D009572:Nitrite Reductases; C080610:nitric-oxide reductase (P450); D009584:Nitrogen; C045951:tungstate