Isolation, purification, and characterization of nitrate reductase from a salt-tolerant Rhodotorula glutinis yeast strain grown in the presence of tungsten.

The salt-tolerant Rhodotorula glutinis yeast strain grew in medium containing nitrate, 1 mM tungsten, and trace amounts of molybdenum (as impurities from the reagents used). Isolation of electrophoretically homogenous preparation of nitrate reductase from the Rh. glutinis cells grown under these growth conditions is described.

[Properties of nitrate reductase from Fusarium oxysporum 11dn1 fungi grown under aerobic and anaerobic conditions].

Production of nitrate reductase was studied in 15 species of microscopic fungi grown on a nitrate-containing 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.

Tungsten-containing enzymes.

The biological importance of tungsten has been fully proved in the last decade due to isolation of a number of tungsten-containing enzymes (W-enzymes) from hyperthermophilic archaea. Tungsten was previously considered only as an antagonist of molybdenum, because the replacement of molybdenum by tungsten (due to their chemical similarity) leads to inactivation of molybdenum-containing enzymes (Mo-enzymes). In addition to the "true W-enzymes" in which tungsten cannot be replaced by molybdenum, recently some enzymes have been isolated which can use either molybdenum or tungsten in the catalytic process.

[Kinetic method of tungsten analysis in tungsten-containing enzymes].

A highly sensitive method for tungsten detection in proteins based on the ability of this metal to catalyze the oxidation of with hydrogen peroxide is described. The method allows determining tungsten in protein samples in the concentration range of -0.05 to -0.

Nitrate reductase and nitrous oxide production by Fusarium oxysporum 11dn1 under aerobic and anaerobic conditions.

The fungus Fusarium oxysporum 11dn1 was found to be able to grow and produce nitrous oxide on nitrate-containing medium in anaerobic conditions. The rate of nitrous oxide formation was three to six orders of magnitude lower than the rates of molecular nitrogen production by common denitrifying bacteria. Acetylene and ammonia did not affect the release of nitrous oxide release.

Stimulation of nitrate reductase activity of the salt-tolerant yeast Rhodotorula glutinis by tungsten in the presence of molybdenum.

Tungsten in the presence of molybdenum stimulates nitrate reductase activity and growth of the salt-tolerant yeast Rhodotorula glutinis on medium with nitrates. Tungsten is not incorporated in proteins possessing nitrate reductase activity. A significant increase in molybdenum cofactor in cells grown on medium with equimolar amounts of molybdenum and tungsten may relate to the stimulatory action of tungsten.