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

---

Query: EC:2.3.3.1 (citrate synthase)
4,488 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Copper and cadmium inhibited the growth as well as citric acid production (depending on the heavy metal concentrations) by citric-acid-producing Aspergillus niger. Activity of citrate synthase was connected with citrate synthesis in the absence as well as in the presence of heavy metals. The activity of aconitase, and both NAD- and NADP-isocitrate dehydrogenases was strongly inhibited by copper. The contents of DNA and proteins in the cells decreased but the contents of lipids and polysaccharides increased considerably in the presence of both heavy metals.
...
PMID:Effect of cadmium and copper on the production of citric acid by Aspergillus niger. 1134 55

In crude cell extracts of the ectomycorrhizal fungus, Suillus bovinus, activities of citrate synthase, aconitase, isocitrate dehydrogenase, succinate dehydrogenase, fumarase, and malate dehydrogenase have been proved and analyzed. Citrate synthase exhibited high affinities for both its substrates: oxaloacetate (Km = 0.018 mM) and acetyl-CoA (Km = 0.014 mM). Aconitase showed better affinity for isocitrate (Km = 0.62 mM) than for citrate (Km = 3.20 mM). Analysis of isocitrate dehydrogenase revealed only small maximum activity (60 nmol x mg protein(-1) x min(-1)), the enzyme being exclusively NADP+-dependent. Using the artificial electron acceptor dichlorophenol indophenol, activity and substrate affinity of succinate dehydrogenase were rather poor. Fumarase proved Fe2+-independent. Its affinity for malate was found higher (Km = 1.19 mM) than that for fumarate (Km = 2.09 mM). High total activity of malate dehydrogenase could be separated by native PAGE into a slowly running species of (mainly) cytosolic (about 80%) and a faster running species of (mainly) mitochondrial origin. Affinities for oxaloacetate of the two enzyme species were found identical within limits of significance (Km = 0.24 mM and 0.22 mM). The assumed cytosolic enzyme exhibited affinity for malate (Km = 5.77 mM) more than one order of magnitude lower than that for oxaloacetate. FPLC on superose 12 revealed only one activity band at a molecular mass of 100 +/- 15 kDa. Activities of 2-oxoglutarate dehydrogenase and of succinyl-CoA synthetase could not be found. Technical problems in their detection, but also existence of an incomplete tricarboxylic acid cycle are considered. Metabolite affinities, maximum activities and pH-dependences of fumarase and of malate dehydrogenase allow the assumption of a reductive instead of oxidative function of these enzymes in vivo.
...
PMID:Tricarboxylic acid cycle enzymes of the ectomycorrhizal basidiomycete, Suillus bovinus. 1142 46

In 1992-1994, a disorder known as the epidemic neuropathy afflicted more than 50,000 Cubans. Three different forms of the illness were identified: epidemic optic neuropathy, peripheral neuropathy and mixed optic and peripheral neuropathy. The causes are still unknown. Skeletal muscle biopsy samples were analyzed by standard histological techniques and by biochemical assays. Elevated activities of citrate synthase, a non-respiratory-chain mitochondrial matrix enzyme, suggested possible mitochondrial proliferation in 7 of the 8 patients. Nicotinamide adenine dinucleotide phosphate (NADP(+)) levels were higher in the patients than in the controls (p = 0.04). Levels of nicotinamide adenine dinucleotide (NAD) and the reduced compounds NADH and NADPH were comparable in patients and controls. Elevations of succinate dehydrogenase and citrate synthase activities and high NADP(+) levels suggest that alterations of mitochondrial functions may be associated with this disorder.
...
PMID:Biochemical studies of patients with Cuban epidemic neuropathy. 1172 Nov 82

Protoplasts from barley (Hordeum vulgare), pea (Pisum sativum), wheat (Triticum aestivum), and spinach (Spinacia oleracea) leaves were fractionated into chloroplast- and mitochondrion-enriched fractions. Pyruvate dehydrogenase complex capacities in mitochondria (mtPDC) and chloroplasts (cpPDC) were measured in appropriate fractions under conditions optimal for each isozyme. The total cellular capacity of PDC was similar in barley and pea but about 50% lower in wheat and spinach. In pea a distribution of 87% mtPDC and 13% cpPDC was found on a cellular basis. In barley, wheat, and spinach the subcellular distribution was the opposite, with about 15% mtPDC and 85% cpPDC. cpPDC activity was constant at about 0.1 nmol cell-1 h-1 in cells from different regions along the developing barley leaf and showed no correlation with developmental patterns of photosynthetic parameters, such as increasing Chl and NADP-glyceraldehyde-3-phosphate dehydrogenase activity. Similarly, the capacity of the mitochondrial isoform did not change during barley leaf development and had a developmental pattern similar to that of citrate synthase and fumarase. Differences in subcellular distribution of PDCs in barley and pea are proposed to be due to differences in regulation, not to changes in isozyme proportions during leaf development or to species-specific differences in phosphorylation state of mtPDC after organelle separation.
...
PMID:Distribution of Pyruvate Dehydrogenase Complex Activities between Chloroplasts and Mitochondria from Leaves of Different Species. 1223 37

Little is known about the role of mitochondrial NADP(+)-isocitrate dehydrogenase (NADP(+)-ICDH) in the heart, where this enzyme shows its highest expression and activity. We tested the hypothesis that in the heart, NADP(+)-ICDH operates in the reverse direction of the citric acid cycle (CAC) and thereby may contribute to the fine regulation of CAC activity (Sazanov and Jackson, FEBS Lett 344: 109-116, 1994). We documented a reverse flux through this enzyme in rat hearts perfused with the medium-chain fatty acid octanoate using [U-(13)C(5)]glutamate and mass isotopomer analysis of tissue citrate (Comte et al., J Biol Chem 272: 26117-26124, 1997). In this study, we assessed the significance of our previous finding by perfusing hearts with long-chain fatty acids and tested the effects of changes in O(2) supply. We showed that under all of these conditions citrate was enriched in an isotopomer containing five (13)C atoms. This isotopomer can only be explained by substrate flux through reversal of the NADP(+)-ICDH reaction, which is evaluated at 3-7% of flux through citrate synthase. Small variations in reversal fluxes induced by low-flow ischemia that mimicked hibernation occurred despite major changes in contractile function and O(2) consumption of the heart as well as citrate and succinate release rates and tissue levels. Our data show a reverse flux through NADP(+)-ICDH and support its hypothesized role in the fine regulation of CAC activity in the normoxic and O(2)-deprived heart.
...
PMID:Reverse flux through cardiac NADP(+)-isocitrate dehydrogenase under normoxia and ischemia. 1223 3

Nia30(145) transformants with very low nitrate reductase activity provide an in vivo screen to identify processes that are regulated by nitrate. Nia30(145) resembles nitrate-limited wild-type plants with respect to growth rate and protein and amino acid content but accumulates large amounts of nitrate when it is grown on high nitrate. The transcripts for nitrate reductase (NR), nitrite reductase, cytosolic glutamine synthetase, and glutamate synthase increased; NR and nitrite reductase activity increased in leaves and roots; and glutamine synthetase activity increased in roots. The transcripts for phosphoenolpyruvate carboxylase, cytosolic pyruvate kinase, citrate synthase, and NADP-isocitrate dehydrogenase increased; phosphoenolpyruvate carboxylase activity increased; and malate, citrate, isocitrate, and [alpha]-oxoglutarate accumulated in leaves and roots. There was a decrease of the ADP-glucose pyrophosphorylase transcript and activity, and starch decreased in the leaves and roots. After adding 12 mM nitrate to nitrate-limited Nia30(145), the transcripts for NR and phosphoenolpyruvate carboxylase increased, and the transcripts for ADP-glucose pyrophosphorylase decreased within 2 and 4 hr, respectively. Starch was remobilized at almost the same rate as in wild-type plants, even though growth was not stimulated in Nia30(145). It is proposed that nitrate acts as a signal to initiate coordinated changes in carbon and nitrogen metabolism.
...
PMID:Nitrate Acts as a Signal to Induce Organic Acid Metabolism and Repress Starch Metabolism in Tobacco. 1223 66

The secretion of organic acid anions from roots has been identified as a mechanism of resistance to Al. However, the process leading to the secretion of organic acid anions is poorly understood. The effect of Al on organic acid metabolism was investigated in two lines of triticale (xTriticosecale Wittmark) differing in Al-induced secretion of malate and citrate and in Al resistance. The site of Al-induced secretion of citrate and malate from a resistant line was localized to the root apices (terminal 5 mm). The levels of citrate (root apices and mature root segments) and malate (mature segments only) in roots increased during exposure to Al, but similar changes were observed in both triticale genotypes. The in vitro activities of four enzymes involved in malate and citrate metabolism (citrate synthase, phosphoenolpyruvate carboxylase, malate dehydrogenase, and NADP-isocitrate dehydrogenase) were similar for sensitive and resistant lines in both root apices and mature root segments. The response of these enzymes to pH did not differ between tolerant and sensitive lines or in the presence and absence of Al. Moreover, cytoplasmic and vacuolar pH were not affected by exposure to Al in either line. Together, these results indicate that the Al-dependent efflux of organic acid anions from the roots of triticale is not regulated by their internal levels in the roots or by the capacity of the root cells to synthesize malate and citrate.
...
PMID:Al-induced efflux of organic acid anions is poorly associated with internal organic acid metabolism in triticale roots. 1277 23

Activities of several metabolic enzymes show distinct patterns of zonation along the intestinal tract of tilapia (Oreochromis niloticus), rainbow trout (Oncorhynchus mykiss) and copper rockfish (Sebastes caurinus). Zonation is species and enzyme specific, with different metabolic activities concentrated in specific areas, and few generalizations can be made. The rockfish show the smallest degree of zonation, with highest activities in the third quarter of the intestine, and shallow gradients to either side, and a general upswing in activity towards the distal end. In the trout, mitochondrial enzyme activities (citrate synthase, glutamate dehydrogenase, malate dehydrogenase) are highest in the pyloric caeca and decrease along the length of the small intestine. This pattern is accentuated for malic enzyme and glucose 6-phosphate dehydrogenase. These enzymes drop precipitously in activity after the first few sections of the small intestine, while other NADP-linked dehydrogenases (isocitrate dehydrogenase, and 6-phosphogluconate dehydrogenase) show moderate activity in pyloric caeca and peak toward the distal section of the small intestine. In tilapia, glutamate dehydrogenase shows a similar decrease as in trout, but citrate synthase peaks towards the distal sections. NADP-dependent dehydrogenases reveal distinct patterns, peaking in different sections of the intestine-malic enzyme in the proximal midsection, glucose 6-phosphate dehydrogenase in the distal mid-section, and isocitrate dehydrogenase in the anal section. Enzyme activities in the stomach of trout and tilapia also show zonation, with the midsection generally displaying the highest activities. A 5-day treatment of tilapia with an intraperitoneal cortisol deposit (25 mg kg(-1) wet mass) drastically alters metabolic performance along the gut in enzyme specific patterns, generally increasing enzyme activities in site-specific arrangements. Cortisol treatment also leads to the expected increases in activities of phosphoenolpyruvate carboxykinase, pyruvate kinase and aspartate aminotransferase in liver, but not in kidney. Aspartate aminotransferase is the only enzyme in brain significantly increased by cortisol treatment. Short-term food deprivation changes enzyme patterns, often resembling those observed after cortisol administration. We conclude that brain, liver and intestinal amino acid metabolism is an important target for cortisol action in fish and that metabolic zonation is a key factor to be reckoned with when analyzing physiological phenomena in the fish intestine.
...
PMID:Metabolic zonation in teleost gastrointestinal tract. Effects of fasting and cortisol in tilapia. 1278 63

To probe the functions of multiple forms of isocitrate dehydrogenase in Saccharomyces cerevisiae, mutants lacking three of the isozymes were constructed and analyzed. Results show that, while the mitochondrial NAD+-dependent enzyme, IDH (composed of Idh1p and Idh2p subunits) is not the major contributor to total isocitrate dehydrogenase activity under any growth condition, loss of IDH produces the most dramatic growth phenotypes. These include reduced growth in the absence of glutamate, as well as an increase in expression of Idp2p (the cytosolic NADP+-dependent enzyme) under some growth conditions. In this study, we have focused on another phenotype associated with loss of IDH, an elevated frequency of petite mutations indicating loss of functional mtDNA. Using mutant forms of IDH with altered active site residues, a correlation was observed between the high frequency of petite mutations and the loss of catalytic activity. Loss of Idp1p (the mitochondrial NADP+-dependent enzyme) and Idp2p contributes to the loss of functional mtDNA, but only in an IDH dysfunctional background. Surprisingly, overexpression of Idp1p, but not of Idp2p, was found to result in an elevated petite frequency independent of the functional state of IDH. This is the first phenotype associated with altered Idp1p. Finally, throughout this study we examined effects of loss of mitochondrial citrate synthase (Cit1p) on isocitrate dehydrogenase mutants, since defects in the CIT1 gene were previously shown to enhance growth of IDH dysfunctional strains on nonfermentable carbon sources. Loss of Cit1p was found to suppress the petite phenotype of strains lacking IDH, suggesting that these phenotypes may be linked.
...
PMID:Multiple cellular consequences of isocitrate dehydrogenase isozyme dysfunction. 1459 66

The activities of the citric acid cycle enzymes were determined in mitochondria isolated from kidneys of relatively young, middle age, and old mice. Aconitase exhibited the most significant decrease in activity with age. The activity of alpha-ketoglutarate dehydrogenase exhibited a modest decrease in activity, while NADP(+)-isocitrate dehydrogenase (NADP(+)-ICD) activity increased moderately with age. Activities of citrate synthase, NAD(+)-isocitrate dehydrogenase (NAD(+)-ICD), succinyl-CoA synthetase (SCS), succinate dehydrogenase (SD), fumarase (FUM), and malate dehydrogenase (MD) were not affected. The molar ratio of the intra-mitochondrial redox indicator, NADPH:NADP(+), was higher in young compared to old animals, while the NADH:NAD(+) molar ratio remained unchanged. It is suggested that an age-related decrease in aconitase activity along with relatively subtle alterations in activities of some other citric acid cycle enzymes are likely to contribute to a decline in the overall efficiency of mitochondrial bioenergetics. The biological consequences of such alterations include age-related fluctuations in the citric acid cycle intermediates, which are precursors of protein synthesis, activators of fatty acid synthesis, and can also act as ligands for orphan G-protein coupled receptors.
...
PMID:Aconitase is the main functional target of aging in the citric acid cycle of kidney mitochondria from mice. 1628 53


<< Previous 1 2 3 4 5 6 7 Next >>

---