Abstract
Nitrate reductase (NR), a key enzyme of nitrate metabolism, is regulated at transcription and post-translation in response to environment at light conditions. Inactivation of NR occurs by phosphorylation followed by the binding with 14-3-3 proteins. We studied Ca2+ independent NR kinase from Brassica campesis . Immediately after transferring plants to darkness , we observed an increase of NR kinase activity. This NR kinase activity was inhibited by 10 mM glucose 6-phosphate (G6P) and Fructose 6-phosphate (F6P) approximately 40 %. NR kinase was fractionated by Resource Q chromatography. The major peak of NR kinase activity from dark treated leaves was much higher than those from light treated leaves. NR kinase in the major peak is inhibited by 10 mM G6P and F6P approximately 40 %, 20 % respectively . Taken together with these findings, results obtained suggest that G6P and F6P may be responsible for regulation of NR kinase activity.
