Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.7.1.2 (nitrate reductase)
 3,861 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We provide evidence to show that the increase in nitrate reductase (NR) transcript level stimulated by red light is mediated via a phosphorylation-dependent step. The light-stimulated enhancement of NR transcript level was significantly inhibited by H-7, a protein kinase inhibitor, whereas okadaic acid (OKA), a phosphatase inhibitor, had no effect. Phorbol myristate acetate (PMA), an activator of protein kinase C (PKC) enhanced the NR transcript level in dark-grown leaves. No correlation between changes in NR transcript level and NR activity (NRA) was observed. Inhibition of NRA by OKA and stimulation by H-7 indicated that NRA is increased by dephosphorylating the enzyme. We have identified a protein kinase (C type) that can phosphorylate the purified NR in vitro without the involvement of other accessory proteins. By in vivo labelling with 32P and immunoprecipitation of NR with NR antibodies it was found that in the presence of OKA most NR protein (NRP) was present in phosphorylated state, while with H-7 the reverse was seen. The red (R) and far-red (FR) light reversible experiments suggested that phytochrome (Pfr, an active form) stimulation of NRA is mediated by dephosphorylation of the enzyme, suggesting that Pfr regulates both NR transcription and NRA via phosphorylation/dephosphorylation steps controlled by separate signal transduction pathways.
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PMID:Phosphorylation/dephosphorylation steps are key events in the phytochrome-mediated enhancement of nitrate reductase mRNA levels and enzyme activity in maize. 870 67

The influence of nitrate and its metabolites on the nitrate reductase (NR) gene expression and its relationship with phytochrome (Pfr) regulation of NR in etiolated maize leaves is examined. Nitrate induction and Pfr stimulation are brought about by independent signalling phenomena. Phorbol myristate acetate (PMA), a stimulator of protein kinase C (PKC), mimicked the effect of red light but could not replace the nitrate requirement for the induction of NR transcript accumulation. This suggests that while PKC-type enzymes may be involved in mediating the Pfr signal, nitrate may follow an independent signalling mechanism. Experiments with 5-hydroxytryptamine (5HT) and lithium ions (Li+), which are known to modulate phosphoinositide (PI) turnover, indicated that in addition to generating Pfr-induced second messengers for PKC activation, PI cycle may also generate other signals which mediate nitrate induction of NR gene expression in the dark. The products of nitrate reduction i.e., nitrite and ammonium ion had inhibitory and stimulatory effects respectively, on NR transcript accumulation. They work mainly at the level of nitrate induction.
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PMID:Roles of nitrate, nitrite and ammonium ion in phytochrome regulation of nitrate reductase gene expression in maize. 1020 69