Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:4.1.1.32 (phosphoenolpyruvate carboxykinase)
 4,204 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A gene (SCPEPCD1) encoding phosphoenolpyruvate carboxylase (PEPC) was isolated from the C-4 monocot sugarcane (Saccharum hybrid var. H32-8560). SCPEPCD1 is ca. 6800 bp long, with 10 exons. The entire gene sequence from -1561 to 262 bp downstream of the putative poly(A) addition signal is reported. A low-level, essentially constitutive pattern of expression, amino acid sequence similarities to other 'housekeeping' PEPC enzymes, and the absence of DNA sequence elements conserved in the upstream region of maize and sorghum C-4-specific PEPC genes indicate that SCPEPCD1 encodes a housekeeping PEPC. Despite this, a motif proposed to act as a phosphorylation site in light-mediated activation of photosynthetic PEPC enzymes [10] is present in the SCPEPCD1 protein; evidence is presented for the presence of this site in other housekeeping PEPC proteins.
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PMID:Structure and expression of a sugarcane gene encoding a housekeeping phosphoenolpyruvate carboxylase. 145 Mar 81

Twenty obese and 20 lean LA/N-cp male rats and 20 male Sprague-Dawley rats were fed a diet containing either 54 percent sucrose or starch for six weeks. After a 14-16 hour fast, rats were killed. Liver and kidney enzyme activities were determined in the LA/N-cp rats while plasma urea and selected amino acids were determined in all rats. Liver glucose-6-phosphatase (G6PASE), fructose-1,6-bisphosphatase (FBPASE), phosphoenolpyruvate carboxykinase (PEPCK), glucose-6-phosphate dehydrogenase (G6PDH), 6-phosphogluconate dehydrogenase (6PGDH), malic enzyme (ME), glucokinase (GK), pyruvate kinase (PK), phosphofructokinase (PFK), glutamic-oxaloacetic-transaminase (GOT), glutamic-pyruvic transaminase (GPT), arginase (ARGASE), arginine-synthase (ARG-SYN) and ornithine transcarbamylase (OTC) levels were significantly affected by phenotype (obese greater than lean). All the above changes in enzyme levels were exaggerated by sucrose-feeding with the exception of PK, PFK, GOT, GPT, ARGASE and ARG-SYN. Kidney cortex G6PASE, PEPCK and ARGASE activities were higher in the obese rats as compared to the lean littermates. Sucrose feeding resulted in higher cortex G6PASE, FBPASE and PEPCK as compared to starch-fed rats. A phenotype effect was noted with plasma glutamate, urea, leucine, isoleucine and valine (obese greater than lean) and a diet effect was seen with aspartate, phenylalanine, leucine and valine (sucrose greater than starch) concentration. Sprague-Dawley rats had higher plasma urea and lower alanine than lean LA/N-cp males. Metabolic obesity in the LA/N-cp rat appears to involve an elevated capacity for pathways of glycolysis, gluconeogensis, lipogenesis and amino acid catabolism in the liver.
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PMID:Effect of dietary carbohydrate on liver and kidney enzyme activities and plasma amino acids in the LA/N-cp rat. 204 12

Exposure of Reuber hepatoma cells (RHC) to 30 and 300 fM human rIL-1 (hurIL-1) for 4 h significantly decreased cytosolic glucocorticoid binding. Scatchard analysis indicated that the 30 and 300 fM doses of hurIL-1 significantly decreased the Bmax (maximum number of available binding sites), but did not alter the Kd (affinity of the glucocorticoid receptor for ligand). The decrease in cytosolic glucocorticoid binding, expressed relative to cytosol protein, did not result from increased intracellular protein in hurIL-1-treated RHC. In addition, the receptor binding reaction in RHC treated with 300 fM hurIL-1 could be resolved only by computer application of a three-parameter model. Sucrose density gradient ultracentrifugation analysis confirmed significantly less untransformed (8 to 10S) receptor-ligand complexes in hurIL-1-treated RHC, which is biologically significant because hurIL-1 (300 fM) also inhibited the glucocorticoid induction of the gluconeogenic enzyme, phosphoenolpyruvate carboxykinase (PEPCK). Altered transformation of the receptor-ligand complex, a possible mechanism of action for hurIL-1-mediated inhibition of PEPCK induction, was examined. However, receptor transformation, verified by in vitro activation by high salt (0.3 M KCl) of glucocorticoid receptor-ligand complexes and subsequent sucrose density gradient ultracentrifugation analysis, was not affected by hurIL-1. Furthermore, cytoplasmic glucocorticoid binding, determined in intact cell dexamethasone uptake experiments, was decreased in hurIL-1-treated RHC. The decrease in cytoplasmic glucocorticoid binding was reflected subsequently in decreased nuclear binding. The results support our hypothesis that, during acute infection and inflammation, mediators alter metabolic pathways in the liver by interfering with glucocorticoid action.
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PMID:Human recombinant IL-1 alters glucocorticoid receptor function in Reuber hepatoma cells. 284 96

Sucrose synthase (SS; EC 2.4.1.13) was radiolabeled in situ by incubating detached soybean nodules with 32Pi. Phosphoamino acid analysis indicated that SS was phosphorylated on a serine residue(s). In-vitro phosphorylation of purified nodule SS by desalted nodule extracts was Ca2+-dependent. This SS-kinase was partially purified (approximately 2200-fold) from nodules harvested from illuminated plants. The molecular mass of the SS-kinase was about 55,000 on a Superdex 75 size-exclusion column or in a denaturing autophosphorylation gel. With either purified nodule SS or Syntide 2 as substrate, exogenous calmodulin and phosphatidylserine showed little or no effect on the in-vitro activity of this partially purified protein kinase. However, its activity was inhibited by W-7. The purified nodule SS-kinase (or CDPK) phosphorylated nodule PEP carboxylase (PEPC; EC 4.1.1.31) in the presence of Ca2+. In contrast, a partially purified nodule PEPC-kinase preparation was incapable of phosphorylating nodule SS. Unlike nodule PEPC [Zhang et al. (1995) Plant Physiol. 108, 1561-1568], the phosphorylation state of SS is not likely modulated in planta by photosynthate supply from the shoots.
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PMID:Seryl-phosphorylation of soybean nodule sucrose synthase (nodulin-100) by a Ca2+-dependent protein kinase. 923 14

Capacities of phosphoenolpyruvate carboxylase (PEP-Co), ribulose bisphosphate carboxylase (Rubisco), NADP+ malic enzyme (ME) and of malate dehydrogenase (MDH) were measured in the Euphorbiacea Aleurites montana, grown under 700 ppm CO2 for four weeks prior to enzyme extraction. For comparison Bryophyllum daigremontiana (CAM). Saccharum officinarum (C4) and Capsicum frutescens (C3) were treated in the same way. PEP-Co capacity of Aleurites was in the range of 12-, that of Capsicum approx. 26 nmol x min(-1) x mg protein(-1), without significant influence of the light period or CO2-treatment. In contrast, the activity of the enzyme from Saccharum was, depending on the duration of light, 160- respectively 96 times higher than that of the tung-oil tree. In Bryophyllum a rather low activity in the morning was increased during the day to approx. 230 nmol x min(-1) x mg protein(-1) in plants grown in the greenhouse and to approx. 115 nmol x min(-1) x mg protein(-1) in those from the growth chamber. Malate was hardly detectable in extracts of Aleurites, whereas it was high in Bryophyllum, depending on the light period. The ratio of average PEP-Co to Rub-Co capacity was high for the CAM-plant (20:1), somewhat lower for sugar cane (10:1), but almost at equality for Aleurites (0.9:1) and chilli (0.8:1). For the NADP+ malic enzyme, low capacity (20 to 28 nmol x min(-1) x mg protein(-1)) was found for Aleurites and for Capsicum, whereas it was 10 to 17 times higher in Saccharum. In Bryophyllum, the activity was up to 80 nmol x min(-1) x mg protein, dependent on light period. MDH capacity was extremely high in all plants investigated. Highest rates (10-20 micromol x min(-1) x mg protein(-1)), were obtained for Bryophyllum, followed by sugar cane and Capsicum with 5-8 micromol x min(-1) x mg protein(-1). Again, the lowest capacity was found in extracts of Aleurites with approx. 1.3 to 1.6 micromol x min(-1) x m protein(-1). Thus, in Aleurites montana no indication for C4- or Crassulacean acid metabolism was obtained. Therefore, the earlier observed very efficient uptake of CO2 cannot be explained by a high expression of the PEP-Co protein, known to occur in CAM- and C4-plants.
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PMID:Capacity of enzymes of the euphorbiacea Aleurites montana involved in CO2-fixation, compared to plants having C3-, C4- and Crassulacean acid metabolism. 1092 49

Transgenic Nicotiana plumbaginifolia plants that express either a 5-fold increase or a 20-fold decrease in nitrate reductase (NR) activity were used to study the relationships between carbon and nitrogen metabolism in leaves. Under saturating irradiance the maximum rate of photosynthesis, per unit surface area, was decreased in the low NR expressors but was relatively unchanged in the high NR expressors compared with the wild-type controls. However, when photosynthesis was expressed on a chlorophyll (Chl) basis the low NR plants had comparable or even higher values than the wild-type plants. Surprisingly, the high NR expressors showed very similar rates of photosynthesis and respiration to the wild-type plants and contained identical amounts of leaf Chl, carbohydrate, and protein. These plants were provided with a saturating supply of nitrate plus a basal level of ammonium during all phases of growth. Under these conditions overexpression of NR had little impact on leaf metabolism and did not stimulate growth or biomass production. Large differences in photochemical quenching and nonphotochemical quenching components of Chl a fluorescence, as well as the ratio of variable to maximum fluorescence, (FV/FM), were apparent in the low NR expressors in comparison with the wild-type controls. Light intensity-dependent increases in nonphotochemical quenching and decreases in FV/FM were greatest in the low NR expressors, whereas photochemical quenching decreased uniformly with increasing irradiance in all plant types. Nonphotochemical quenching was increased at all except the lowest irradiances in the low NR expressors, allowing photosystem II to remain oxidized on its acceptor side. The relative contributions of photochemical and nonphotochemical quenching of Chl a fluorescence with changing irradiance were virtually identical in the high NR expressors and the wild-type controls. Zeaxanthin was present in all leaves at high irradiances; however, at high irradiance leaves from the low NR expressors contained considerably more zeaxanthin and less violaxanthin than wild-type controls or high NR expressors. The leaves of the low NR expressors contained less Chl, protein, and amino acids than controls but retained more carbohydrate (starch and sucrose) than the wild type or high NR expressors. Sucrose phosphate synthase activities were remarkably similar in all plant types regardless of the NR activity. In contrast phosphoenolpyruvate carboxylase activities were increased on a Chl or protein basis in the low NR expressors compared with the wild-type controls or high NR expressors. We conclude that large decreases in NR have profound repercussions for photosynthesis and carbon partitioning within the leaf but that increases in NR have negligible effects.
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PMID:Adaptations of Photosynthetic Electron Transport, Carbon Assimilation, and Carbon Partitioning in Transgenic Nicotiana plumbaginifolia Plants to Changes in Nitrate Reductase Activity. 1223 70

In this study it is shown that at least 10% of the major storage product of developing embryos of Brassica napus (L.), triacylglycerol, is lost during the desiccation phase of seed development. The metabolism of this lipid was studied by measurements of the fate of label from [1-(14)C]decanoate supplied to isolated embryos, and by measurements of the activities of enzymes of fatty acid catabolism. Measurements on desiccating embryos have been compared with those made on embryos during lipid accumulation and on germinating seedlings. Enzymes of beta-oxidation and the glyoxylate cycle, and phosphoenolpyruvate carboxykinase were present in embryos during oil accumulation, and increased in activity and abundance as the seeds matured and became desiccated. Although the activities were less than those measured during germination, they were at least comparable to the in vivo rate of fatty acid synthesis in the embryo during development. The pattern of labelling, following metabolism of decanoate by isolated embryos, indicated a much greater involvement of the glyoxylate cycle during desiccation than earlier in oil accumulation, and showed that much of the (14)C-label from decanoate was released as CO(2) at both stages. Sucrose was not a product of decanoate metabolism during embryo development, and therefore lipid degradation was not associated with net gluconeogenic activity. These observations are discussed in the context of seed development, oil yield, and the synthesis of novel fatty acids in plants.
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PMID:Storage oil breakdown during embryo development of Brassica napus (L.). 1576 24

The regulation of carbon partitioning between carbohydrates (principally sucrose) and amino acids has been only poorly characterized in higher plants. The hypothesis that the pathway of sucrose and amino acid biosynthesis compete for carbon skeletons and energy is widely accepted. In this review, we suggest a mechanism involving the regulation of cytosolic protein kinases whereby the flow of carbon is regulated at the level of partitioning between the pathways of carbohydrate and nitrogen metabolism via the covalent modulation of component enzymes. The addition of nitrate to wheat seedlings (Triticum aestivum) grown in the absence of exogenous nitrogen has a dramatic, if transient, impact on sucrose formation and on the activities of sucrose phosphate synthase (which is inactivated) and phosphoenolpyruvate carboxylase (which is activated). The activities of these two enzymes are modulated by protein phosphorylation in response to the addition of nitrate, but they respond in an inverse fashion. Sucrose phosphate synthase in inactivated and phosphoenolpyruvate carboxylase is activated. Nitrate functions as a signal metabolite activating the cytosolic protein kinase, thereby modulating the activities of at least two of the key enzymes in assimilate partitioning and redirecting the flow of carbon away from sucrose biosynthesis toward amino acid synthesis.
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PMID:Nitrate activation of cytosolic protein kinases diverts photosynthetic carbon from sucrose to amino Acid biosynthesis: basis for a new concept. 1665 3

After a 5-second exposure of illuminated bermudagrass (Cynodon dactylon L. var. ;Coastal') leaves to (14)CO(2), 84% of the incorporated (14)C was recovered as aspartate and malate. After transfer from (14)CO(2)-air to (12)CO(2)-air under continuous illumination, total radioactivity decreased in aspartate, increased in 3-phosphoglyceric acid and alanine, and remained relatively constant in malate. Carbon atom 1 of alanine was labeled predominantly, which was interpreted to indicate that alanine was derived from 3-phosphoglyceric acid. The activity of phosphoenolpyruvate carboxylase, alkaline pyrophosphatase, adenylate kinase, pyruvate-phosphate dikinase, and malic enzyme in bermudagrass leaf extracts was distinctly higher than those in fescue (Festuca arundinacea Schreb.), a reductive pentose phosphate cycle plant. Assays of malic enzyme activity indicated that the decarboxylation of malate was favored. Both malic enzyme and NADP(+)-specific malic dehydrogenase activity were low in bermudagrass compared to sugarcane (Saccharum officinarum L.). The activities of NAD(+)-specific malic dehydrogenase and acidic pyrophosphatase in leaf extracts were similar among the plant species examined, irrespective of the predominant cycle of photosynthesis. Ribulose-1, 5-diphosphate carboxylase in C(4)-dicarboxylic acid cycle plant leaf extracts was about 60%, on a chlorophyll basis, of that in reductive pentose phosphate cycle plants.We conclude from the enzyme and (14)C-labeling studies that bermudagrass contains the C(4)-dicarboxylic acid cycle and that pyruvate-phosphate dikinase does not exist exclusively in C(4)-dicarboxylic acid cycle plants, and we propose that in C(4)-dicarboxylic acid cycle plants the transfer of carbon from a dicarboxylic acid to 3-phosphoglyceric acid involves a decarboxylation reaction and then a refixation of carbon dioxide by ribulose-1, 5-diphosphate carboxylase.
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PMID:Photosynthetic CO(2) Fixation Products and Activities of Enzymes Related to Photosynthesis in Bermudagrass and Other Plants. 1665 95

The specific phosphatase, sucrose phosphate phosphohydrolase (sucrose phosphatase, EC 3.1.3.24) was present in vacuole preparations from storage tissue of red beet (Beta vulgaris L.), sugar beet (Beta vulgaris L. cultivar Kawemono), and immature sugarcane (Saccharum spp. hybrid, cultivar NCO 310). In red beet vacuole preparations the specific activity of sucrose phosphatase, using the naturally occurring vacuole marker, betanin, as reference, was higher than the specific activity of cytoplasmic markers, phosphoenolpyruvate carboxylase and glucose 6-phosphate dehydrogenase, suggesting that sucrose phosphatase is associated with the vacuoles. High speed centrifugation of lysed vacuoles did not result in precipitation of the enzyme indicating that the enzyme is not tightly bound to the tonoplast. Sucrose phosphatase was more sensitive to inhibition by sodium vanadate and less sensitive to ammonium molybdate than was the nonspecific phosphatase which was also present in the extracts. Sucrose phosphatase might be part of the group translocator proposed recently to operate in the tonoplast of sugarcane and red beet.
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PMID:Sucrose phosphatase associated with vacuole preparations from red beet, sugar beet, and immature sugarcane stem. 1666 98


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