The assimilatory nitrate reductase [NAD (P) H: nitrate oxidoreductase, EC 18.104.22.168] of the nitrate-utilizing yeast Candida utilis was prepared in soluble form from cells grown aerobically with nitrate as the nitrogen source, and some of its properties studied. The enzyme is cytoplasmic in intracellular distribution and its activity is NAD (P) H-dependent. The enzyme utilized both NADH and NADPH as electron donors but not reduced viologen dyes, flavins and other reductants. Flavin compounds, at higher concentrations, decreased the enzyme activity, while at very low concentrations, FAD (10-5 M) showed little stimulation. The optimal activity of the enzyme was obtained when the reaction was carried out for 10 min at 37° C at pH 7·0 with 20 mM KNO3, 0·1 mM NAD (P) H, 0.01 mM FAD and 140 μg enzyme protein. Complete loss of enzyme activity was observed on exposure to 50° C for 3 min. pHMB, cyanide, azide and EDTA, in that order, inhibited the enzyme activity effectively. The inhibition caused by pHMB was largely reversed by DTT.
|Original language||English (US)|
|Number of pages||11|
|Journal||Proceedings of the Indian Academy of Sciences - Section B|
|State||Published - May 1976|
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)
- Agricultural and Biological Sciences(all)