Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:4.1.1.49 (phosphoenolpyruvate carboxykinase)
4,654 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Pyruvate orthophosphate dikinase, phosphoenolpyruvate carboxylase, and NADP-malate dehydrogenase function in a series of reactions for fixing CO2 in mesophyll cells and NADP-malic enzyme (ME) catalyzes the production of CO2 and NADPH in bundle sheath cells of maize which is a NADP-ME type C4 plant. Northern blot analyses with cDNA clones for pyruvate orthophosphate dikinase and phosphoenolpyruvate carboxylase and in vitro translation-immunoprecipitation experiments with antiserum to NADP-malate dehydrogenase showed that pools of transcripts of these three genes grow and shrink coordinately in mesophyll cells but not in bundle sheath cells upon illumination of dark-grown maize seedlings. Western blot analyses indicated that the protein levels of phosphoenolpyruvate carboxylase and pyruvate orthophosphate dikinase are low in dark-grown maize seedlings and increase progressively following light-induced transient accumulation of their mRNAs in mesophyll cells. These proteins continue to accumulate and plateau in late-greening and green leaves in spite of a rapid drop in the sizes of their mRNA pools. Surprisingly, relatively large amounts of NADP-malate dehydrogenase are present in mesophyll cells of etiolated leaves despite the low level of the corresponding mRNA. No phosphoenolpyruvate carboxylase or NADP-malate dehydrogenase were detected in bundle sheath cells. On the other hand, the ME gene responds to light induction at both the transcriptional and translational levels only in bundle sheath cells. Moreover, the steady-state level of ME mRNA stays high in late-greening and green leaves in contrast to the rapid decline of mRNA levels of three other C4 pathway genes in mesophyll cells. In addition, low levels of both the mRNA and protein encoded by the PPDK gene were detected in bundle sheath cells. These levels were not influenced by light as distinguished from the patterns observed in mesophyll cells.
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PMID:Differential expression of C4 pathway genes in mesophyll and bundle sheath cells of greening maize leaves. 244 51

1. The activities of phosphoenolpyruvate carboxykinase, malic enzyme, NAD+ and NADP+ isocitrate isocitrate dehydrogenase, glucose-6-phosphate dehydrogenase, lactate dehydrogenase and pyruvate kinase were assayed in homogenate of camel hump and sheep tail tissues. 2. In addition the levels of glucose, cholesterol, total protein and total lipids in these tissues were measured. 3. Results obtained were utilized to compare the state of metabolism of adipose tissue of camel hump to that of sheep tail, and to shed some light on possible contribution of these tissues toward blood glucose level.
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PMID:A comparative study of enzyme profile of camel (Camelus dromedarius) hump and sheep (Ovis aries) tail tissues. 280 43

A major difference between the metabolism of Leishmania species amastigotes and cultured promastigotes was found in the area of CO2 fixation and phosphoenolpyruvate metabolism. Malate dehydrogenase (EC 1.1.1.37) and phosphoenolpyruvate carboxykinase (EC 4.1.1.49) were at much higher activities in amastigotes than promastigotes of both L. m. mexicana and L. donovani, whereas the reverse was true of pyruvate kinase (EC 2.7.1.40). Pyruvate carboxylase (EC 6.4.1.1) and malic enzyme (carboxylating) (EC 1.1.1.40) could not be detected in L. m. mexicana amastigotes. Promastigotes of L. m. mexicana had a high NAD-linked glutamate dehydrogenase activity in comparison to amastigotes, whereas NADP-linked glutamate dehydrogenase activity was detected only in amastigotes. Leishmania m. mexicana culture promastigotes were killed in vitro by the trivalent antimonial Triostam (LD50, 20 micrograms/ml) and the trivalent arsenical melarsen oxide (LD50, 20 micrograms/ml), but they were unaffected by Pentostam. Neither antimonial drug significantly inhibited leishmanial hexokinase (EC 2.7.1.2), phosphofructokinase (EC 2.7.1.11), pyruvate kinase, malate dehydrogenase or phosphoenolpyruvate carboxykinase, whereas melarsen oxide was a potent inhibitor of all the enzymes tested except phosphoenolpyruvate carboxykinase.
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PMID:Leishmania mexicana: enzyme activities of amastigotes and promastigotes and their inhibition by antimonials and arsenicals. 298 38

Sand rats (Psammomys obesus) maintained on a diet providing a free choice between laboratory chow and salt bush (Atriplex halimus) were classified into four groups differing in extent of the diabetic syndrome: A, normoglycemic-normoinsulinemic; B, normoglycemic-hyperinsulinemic; C, hyperglycemic-hyperinsulinemic; or D, hyperglycemic with reduced insulin levels. The metabolic pattern of these groups was characterized by measuring the uptake of fatty acid-labeled, very-low-density lipoprotein-borne triglycerides (VLDL-TG) and [3H]-2-deoxyglucose (2-DOG) into muscle and adipose tissues; incorporation of [14C]alanine into glycogen in vivo; gluconeogenesis from lactate, pyruvate, and alanine in hepatocytes; the effect of insulin on glycogen synthesis from glucose; the oxidation of albumin-bound [1-14C]palmitate and [14C]glucose in strips of soleus muscle; activities of muscle and adipose tissue lipoprotein lipase; and activities of rate-limiting enzymes of glycolysis, gluconeogenesis, and fatty acid synthesis in liver. In group A, uptake of VLDL-TG and activity of lipoprotein lipase were higher in adipose tissue and lower in muscle than in albino rats. In the liver, gluconeogenesis and the activity of phosphoenolpyruvate carboxykinase, as well as lipid synthesis and the activity of NADP-malate dehydrogenase, were higher than in albino rats, whereas activity of pyruvate kinase was lower. In group B, uptake of VLDL-TG by adipose tissue and muscle and lipoprotein lipase activity were similar or higher than in group A. Uptake of 2-DOG by muscle and adipose tissue and activity of liver phosphoenolpyruvate carboxykinase were lower than in group A. In groups C and D, uptake of VLDL-TG and lipoprotein lipase activity in muscle were further increased.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Characterization of stages in development of obesity-diabetes syndrome in sand rat (Psammomys obesus). 351 25

A comparison of glucose catabolism by juvenile and adult liver flukes, Fasciola hepatica, showed that in the adult the cytosolic degradation of glucose via phosphoenolpyruvate carboxykinase (PEPCK) was the most important route, whereas in the freshly excysted juvenile a large part was degraded via pyruvate kinase (PK). However, it was also shown that the adult did not exclusively use the PEPCK pathway, nor did the juvenile exclusively use the PK pathway. When the juvenile was forced to anaerobic functioning it produced propionate and acetate just like the adult, but this did not imply that it switched to the pathways of the adult: the pathway via PK remained important. Malic enzyme (NADP(H)-dependent) was demonstrated to be present in the cytosol and in the mitochondria of both juveniles and adults. These enzyme activities enable the parasite to use a mixture of malate and pyruvate in any ratio as substrate for the mitochondrial production of propionate and acetate. Pyruvate dismutation was important in the anaerobically functioning juvenile, whereas in the adult malate was the major, but not the only mitochondrial substrate. The pH profiles of PK and PEPCK showed that the pathway of PEP metabolism at the PK/PEPCK branchpoint can be regulated by the pH. However, the end products of glucose breakdown were not dependent on the pH. During its development, the liver fluke will gradually be forced to anaerobic functioning. At first, the acidic end product will favour a partitioning of PEP at the PK/PEPCK branchpoint towards malate formation. Later, a lasting predominance of the PEPCK pathway occurs as PK activity almost completely disappears.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Differences in intermediary energy metabolism between juvenile and adult Fasciola hepatica. 362 72

The metabolism of glycerate and aspartate was investigated in perfused rat kidneys. The major pathway active for aspartate metabolism and NH3 production was found to include transamination, and not the purine nucleotide cycle. Pyruvate cycling was identified as a means by which reducing potential is generated in the cytosol for glucose and lactate production from these substrates. Inhibition of mitochondrial pyruvate transport caused an inhibition of glucose production, accumulation of lactate and pyruvate in the perfusate, and a decrease in the [lactate]/[pyruvate] ratio in kidneys perfused with aspartate. These data indicate a role of mitochondrial pyruvate transport in the provision of cytosolic reducing potential. With either aspartate or glycerate, 3-mercaptopicolinic acid (3-MPA) suppressed glucose synthesis and caused accumulation of malate plus fumarate within the kidney. Glucose production from glycerate was much less sensitive to the presence of 3-MPA than was glucose production from aspartate, illustrating a phosphoenolpyruvate carboxykinase (PEPCK)-independent pathway for the cycling of pyruvate. In aspartate-perfused kidneys, the presence of 3-MPA, at concentrations that completely blocked glucose accumulation in the perfusate, did not affect the rate of NH3 production and had only a minor effect on the rate of aspartate uptake. These data allow for an estimation of the rate of pyruvate formation from aspartate of about 1 mumol/min per kidney under conditions of complete PEPCK inhibition. Thus a PEPCK-independent pathway is operative for amino acid oxidation and pyruvate formation in perfused kidneys. The NADP-linked, but not the NAD-linked, 'malic' enzyme activity of the kidney cortex was found to be sufficient to catalyse this estimated rate of pyruvate formation.
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PMID:The involvement of pyruvate cycling in the metabolism of aspartate and glycerate by the perfused rat kidney. 380 Sep 11

The effects of endotoxin administration on glycolytic and tricarboxylic acid cycle intermediates in dog livers were studied. Changes in metabolite concentrations were expressed graphically as percentages of controls using "crossover" plots in order to identify transitory rate-controlling steps. The results show that endotoxin administration increased glycolytic flux through pyruvate kinase, inhibited gluconeogenic flux through phosphoenolpyruvate carboxykinase, decreased glycogen storage, shifted cytosolic and mitochondrial redox state from a relatively oxidized to a more reduced state, decreased the extra- and intramitochondrial malate-aspartate and glutamate-alpha-ketoglutarate shuttle activities, depleted ATP, ADP, and NADP concentrations, and decreased energy charge. Based on these data, it is concluded that pyruvate kinase plays the major role in the control of glycolysis, while phosphoenolpyruvate carboxykinase is the major controlling step for the regulation of gluconeogenesis in dog livers during endotoxic shock. In addition, the major factor in the regulation of metabolic pathways that produce and utilize high-energy phosphates in the livers was impaired in endotoxic shock.
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PMID:Glycolytic and tricarboxylic acid cycle intermediates in dog livers during endotoxic shock. 409 20

Fat-cells were prepared from rat and guinea-pig epididymal adipose tissue and compared on the basis of the intracellular distributions and activities of enzymes and with respect to their utilization of various U-(14)C-labelled substrates for lipogenesis. 1. Compared with the rat, guinea-pig extramitochondrial enzyme activities differed in that aconitate hydratase, alanine aminotransferase, ATP-citrate lyase, lactate dehydrogenase, NAD-malate dehydrogenase, NADP-malate dehydrogenase and phosphoenolpyruvate carboxykinase activities were appreciably lower, whereas aspartate aminotransferase, glucose 6-phosphate dehydrogenase, NADP-isocitrate dehydrogenase and 6-phosphogluconate dehydrogenase activities were appreciably higher. Mitochondrial activities of citrate synthase, NADP-isocitrate dehydrogenase and pyruvate carboxylase were appreciably lower, whereas mitochondrial activities of aspartate aminotransferase, glutamate dehydrogenase, NAD-malate dehydrogenase and phosphoenolpyruvate carboxykinase were higher in the guinea pig compared with the rat. 2. In general guinea-pig fat-cells incorporated acetate and lactate into fatty acids more readily than rat fat-cells, whereas rat fat-cells incorporated glucose and pyruvate more readily than guinea-pig fat-cells. 3. Acetate stimulated the incorporation of glucose into fatty acids in rat fat-cells, but had no appreciable effect upon this process in guinea-pig fat-cells. Acetate greatly decreased the incorporation of lactate into fatty acids in cells from both species. 4. Lactate/pyruvate ratios produced by incubation of guinea-pig cells with glucose+insulin were very low compared with those found with rat cells under the same conditions. 5. With glucose (+insulin) or with glucose+acetate (+insulin) as substrates guinea-pig cells produced enough NADPH by the hexose monophosphate pathway to satisfy the NADPH requirements of lipogenesis. In rat fat-cells under the same conditions, hexose monophosphate-pathway NADPH provision was not sufficient to meet the requirements of lipogenesis. 6. These results are discussed, particularly in relationship to the disposition of cytosolic reducing equivalents in the cells.
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PMID:Lipogenesis in rat and guinea-pig isolated epididymal fat-cells. 415 67

1. Foetal rat liver slices incorporate the C-3 of aspartate and C-2 of glutamate into fatty acids at rates equal to those observed with adult rat liver slices. Incorporation of either of these labelled carbon atoms into fatty acids would require a functioning citrate-cleavage pathway which consists of the enzymes ATP-citrate lyase, NAD-malate dehydrogenase and NADP-malate dehydrogenase. However, NADP-malate dehydrogenase is present in foetal rat liver at only 5% of the activity detectable in adult rat liver. 2. From these findings and the effect of cofactors on the formation of (14)CO(2) from [1,5-(14)C(2)]citrate in liver supernatant fractions (100000g), it is suggested that NADP-malate dehydrogenase limits the citrate-cleavage sequence. 3. Measurement of the citrate-cleavage pathway by incorporation studies with [3-(14)C]aspartate and [U-(14)C]glucose and by determining the activities of ATP-citrate lyase and NADP-malate dehydrogenase have shown that this sequence of reactions is present in the liver of the bovine foetus but not in the adult. However, C-2 of glutamate is not incorporated into fatty acids or non-saponifiable lipid by bovine liver slices. This finding as well as those presented above for the adult and foetal rat liver are interpreted on the basis of a competition between phosphoenolpyruvate carboxykinase and NAD-malate dehydrogenase for oxaloacetate produced by the cleavage of citrate in the cytosol.
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PMID:The metabolic fate of the products of citrate cleavage. Adenosine triphosphate-citrate lyase and nicotinamide-adenine dinucleotide phosphate-linked malate dehydrogenase in foetal and adult liver from ruminants and non-ruminants. 438 7

1. Fat-cells isolated from rabbit perirenal adipose tissue were incubated with the following U-(14)C-labelled substrates: 5mm-glucose (+insulin), 5mm-pyruvate, 5mm-lactate, 5mm-glucose+5mm-acetate (+insulin), and the relative rates of incorporation of these substrates into glyceride fatty acids determined. In general total rates of fatty acid synthesis were similar whatever substrate was supplied to the cells. 2. Rabbit fat-cells incorporated [U-(14)C]acetate into fatty acids and CO(2) as well in the absence of glucose as in the presence of this substrate. 3. The disposition of the utilization of glucose-derived carbon through various metabolic pathways was determined. 4. Extramitochondrial and mitochondrial activities were determined for 11 enzymes. The cells contained a very low activity of pyruvate carboxylase, undetectable NADP-malate dehydrogenase activity and a high mitochondrial phosphoenolpyruvate carboxylase activity. 5. Various rabbit fat-cell metabolic parameters based on the measurement of (14)C incorporation and enzyme activity were compared with the same parameters previously measured in rat and guinea-pig fat-cells. In general guinea pig occupied a position between rat and rabbit with respect to these parameters. 6. The profiles of substrate incorporation into fatty acids and of relative enzyme activities in rabbit fat-cells indicated that the operation of a ;citrate-cleavage' pathway may not be obligatory for the supply of lipogenic acetyl units.
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PMID:Lipogenesis in rabbit isolated fat-cells. 447 91


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