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. The isolated nitrate reductase is a molybdenum-containing homodimer with molecular mass of 130 kD, containing 0.177 mol of Mo per mol of the enzyme. The activity of the enzyme is maximal at pH 7.0 and 35–45°C and is inhibited by low concentrations of azide and cyanide. The enzyme is almost insensitive to 1 mM tungsten.