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)

Plant 3-hydroxy-3-methylglutaryl-CoA reductase(HMGR; EC 1.1.1.34) and sucrose-phosphate synthase (SPS; EC 2.4.1.14) and synthetic peptides designed from the known phosphorylation sites of plant HMGR (SAMS*: KSHMKYNRSTKDVK), rat acetyl-CoA carboxylase (SAMS: HMRSAMSGLHLVKRR), spinach SPS (SP2: GRRJRRISSVEJJDKK), and spinach NADH:nitrate reductase (NR6: GPTLKRTASTPFJNTTSK) were used to characterize kinase activities from cauliflower (Brassica oleracea L. ) inflorescences. The three major peaks of protein kinase activity resolved by anion-exchange FPLC are homologs of those observed previously in spinach leaves and thus are designated PKI, PKIV, and PKIII, listed in order of elution. PKIV was the most active in terms of phosphorylation and inactivation of recombinant Nicotiana HMGR and was also strictly Ca2+ dependent. The novel aspects are that PKIII has not been detected in previous cauliflower studies, that SAMS* is a more specific peptide substrate to identify potential HMGR kinases, and that the major HMGR kinase in cauliflower is Ca2+ dependent. Of the three major kinases that phosphorylated the SP2 peptide only PKI (partially Ca2+ sensitive) and PKIII (Ca2+ insensitive) inactivated native spinach leaf SPS. Cauliflower extracts contained endogenous SPS that was inactivated by endogenous kinase(s) in an ATP-dependent manner and this may be one of the substrate target proteins for PKI and/or PKIII. The substrate specificity of the three kinase peaks was studied using synthetic peptide variants of the SP2 sequence. All three kinases had a strong preference for peptides with a basic residue at P-6 (as in SP2 and SAMS*; SAMS has a free amino terminus at this position) or a Pro at P-7 (as in NR6). This requirement for certain residues at P-6 or P-7 was not recognized in earlier studies but appears to be a general requirement. In plant HMGR, a conserved His residue at P-6 is involved directly in catalysis and this may explain why substrates reduced HMGR phosphorylation in vitro.
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PMID:3-Hydroxy-3-methylglutaryl-coenzyme A reductase kinase and sucrose-phosphate synthase kinase activities in cauliflower florets: Ca2+ dependence and substrate specificities. 967 40

SNF1-related protein kinases (SnRKs) are widely conserved in plants. Previous studies have shown that members of the SnRK1 subfamily phosphorylate and inactivate at least four important plant metabolic enzymes: 3-hydroxy-3-methylglutaryl-CoA reductase, sucrose phosphate synthase, nitrate reductase, and trehalose phosphate synthase 5. In this paper, we demonstrate that two SnRK1 proteins of potato, PKIN1 and StubSNF1, interact with a cytosolic pyruvate kinase (PK(c)) of potato in a yeast two-hybrid assay. The interacting domain of PK(c) is located in its C-terminal region and contains the putative SnRK1 recognition motif ALHRIGS(500)ASVI. Our results indicate that both SnRK1s influence PK(c) activity in vivo. Antisense repression of SnRK1s alters the intensity and light/dark periodicity of PK activity in leaves. However, the differences between PK activity curves in antisense PKIN1 and antisense StubSNF1 lines indicated that the function of the two kinases is not identical in potato.
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PMID:Interaction between SNF1-related kinases and a cytosolic pyruvate kinase of potato. 2043 34