Isolation, Purification, and Characterization of Nitrate Reductase from a Salt-Tolerant Rhodotorula glutinis Yeast Strain Grown in the Presence of Tungsten

Abstract

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 degrees C and is inhibited by low concentrations of azide and cyanide. The enzyme is almost insensitive to 1 mM tungsten.

Nitrate reductase 15N discrimination in Arabidopsis thaliana, Zea mays, Aspergillus niger, Pichea angusta, and Escherichia coli

“…The NR K m for NO − 3 in Arabidopsis and maize ranges from 15 to 40 μM (Su et al, 1997; Campbell, 1999), 199 μM for Aspergillus (Gilliam et al, 1993), and 470 μM for the dissimilatory NR in E. coli (Adams and Mortenson, 1982). There is no information for the specific yeast NR used in our study, but NRs from other genera of yeast have a K m ranging from 110 (Hipkin et al, 1986) to 740 μM (Morozkina et al, 2005). …”