Properties of nitrate reductase from Fusarium oxysporum 11dn1 fungi grown under anaerobic conditions

Abstract

Production of nitrate reductase was studied in 15 species of microscopic fungi grown on a nitratecontaining medium. Experiments were performed with Fusarium oxysporum 11dn1, a fungus capable of producing nitrous oxide as the end product of denitrification. Moreover, a shift from aerobic to anaerobic conditions of growth was accompanied by a sharp increase in the activity of nitrate reductase. Studies of nitrate reductase from the mycelium of Fusarium oxysporum 11dn1, grown under aerobic and anaerobic conditions, showed that this enzyme belongs to molybdenum-containing nitrate reductases. The enzymes under study differed in the molecular weight, temperature optimum, and other properties. Nitrate reductase from the mycelium grown under aerobic conditions was shown to belong to the class of assimilatory enzymes. However, nitrate reductase from the mycelium grown anaerobically had a dissimilatory function. An increase in the activity of dissimilatory nitrate reductase, observed under anaerobic conditions, was associated with de novo synthesis of the enzyme.Abbreviations : BPB, bromophenol blue; MV, methyl viologen; NRase, nitrate reductase; NIRase, nitrite reductase; NORase, nitric oxide reductase; PMSF, phenylmethylsulfonyl fluoride.

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“…For example, Morozkina et al . () reported that Fusarium oxysporum 11dn1, which grows well in both aerobic and anaerobic conditions, has a nitrate reductase in the mycelium, showing assimilatory function under aerobic conditions and dissimilatory nitrate reduction under the anaerobic conditions. Stanić et al .…”

“…Only a few studies have been reported regarding facultatively anaerobic fungi, and these studies have shown variable distrategies in response to oxygen presence or absence. For example, Morozkina et al (2005) reported that Fusarium oxysporum 11dn1, which grows well in both aerobic and anaerobic conditions, has a nitrate reductase in the mycelium, showing assimilatory function under aerobic conditions and dissimilatory nitrate reduction under the anaerobic conditions. Stanić et al (2013) reported that some anaerobic fungi have complex respiratory chains, containing alternative oxidases that enable electrons to bypass electron transport chains when necessary.…”