Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.4.1.2 (glutamate dehydrogenase)
 4,380 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Several important metabolic functions of the mammalian liver have been shown to be located in zones with respect to the complex microcirculation of the organ. The zonal distribution of the cytosolic component of the acetyl-CoA synthetase activity has been investigated using the dual-digitonin-pulse-perfusion technique, which allows highly zone-selective sampling of cytosol from the periportal and perivenous zone of rat liver. Approximately 80% of the cytosolic enzymes are eluted from the hepatocytes in the periportal and perivenous sub-zones affected by digitonin, while less than 1% of the glutamate dehydrogenase activity (a marker enzyme of the mitochondrial compartment) is eluted. A twofold higher activity of the cytosolic form of acetyl-CoA synthetase is found in the periportal zone compared to the perivenous zone in fed male rats. Following a fasting/refeeding transition, this activity gradient is abolished in a manner similar to that observed for the enzyme acetyl-CoA carboxylase. Since the latter enzyme is utilizing the product of acetyl-CoA synthetase, acetyl-CoA, the similarity in the observed regulation suggests a functional coupling between cytosolic acetate activation and fatty-acid synthesis.
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PMID:Periportal zonation of the cytosolic acetyl-CoA synthetase of male rat liver. 134 65

1. A method is described for extracting separately mitochondrial and extramitochondrial enzymes from fat-cells prepared by collagenase digestion from rat epididymal fat-pads. The following distribution of enzymes has been observed (with the total activities of the enzymes as units/mg of fat-cell DNA at 25 degrees C given in parenthesis). Exclusively mitochondrial enzymes: glutamate dehydrogenase (1.8), NAD-isocitrate dehydrogenase (0.5), citrate synthase (5.2), pyruvate carboxylase (3.0); exclusively extramitochondrial enzymes: glucose 6-phosphate dehydrogenase (5.8), 6-phosphogluconate dehydrogenase (5.2), NADP-malate dehydrogenase (11.0), ATP-citrate lyase (5.1); enzymes present in both mitochondrial and extramitochondrial compartments: NADP-isocitrate dehydrogenase (3.7), NAD-malate dehydrogenase (330), aconitate hydratase (1.1), carnitine acetyltransferase (0.4), acetyl-CoA synthetase (1.0), aspartate aminotransferase (1.7), alanine aminotransferase (6.1). The mean DNA content of eight preparations of fat-cells was 109mug/g dry weight of cells. 2. Mitochondria showing respiratory control ratios of 3-6 with pyruvate, about 3 with succinate and P/O ratios of approaching 3 and 2 respectively have been isolated from fat-cells. From studies of rates of oxygen uptake and of swelling in iso-osmotic solutions of ammonium salts, it is concluded that fat-cell mitochondria are permeable to the monocarboxylic acids, pyruvate and acetate; that in the presence of phosphate they are permeable to malate and succinate and to a lesser extent oxaloacetate but not fumarate; and that in the presence of both malate and phosphate they are permeable to citrate, isocitrate and 2-oxoglutarate. In addition, isolated fat-cell mitochondria have been found to oxidize acetyl l-carnitine and, slowly, l-glycerol 3-phosphate. 3. It is concluded that the major means of transport of acetyl units into the cytoplasm for fatty acid synthesis is as citrate. Extensive transport as glutamate, 2-oxoglutarate and isocitrate, as acetate and as acetyl l-carnitine appears to be ruled out by the low activities of mitochondrial aconitate hydratase, mitochondrial acetyl-CoA hydrolyase and carnitine acetyltransferase respectively. Pathways whereby oxaloacetate generated in the cytoplasm during fatty acid synthesis by ATP-citrate lyase may be returned to mitochondria for further citrate synthesis are discussed. 4. It is also concluded that fat-cells contain pathways that will allow the excess of reducing power formed in the cytoplasm when adipose tissue is incubated in glucose and insulin to be transferred to mitochondria as l-glycerol 3-phosphate or malate. When adipose tissue is incubated in pyruvate alone, reducing power for fatty acid, l-glycerol 3-phosphate and lactate formation may be transferred to the cytoplasm as citrate and malate.
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PMID:The intracellular localization of enzymes in white-adipose-tissue fat-cells and permeability properties of fat-cell mitochondria. Transfer of acetyl units and reducing power between mitochondria and cytoplasm. 439 82

The present study evaluates the expression of genes of Giardia lamblia, one of the most simple and most early diverging eukaryotes, that encode the metabolic enzymes pyruvate: ferredoxin oxidoreductase (PFOR), acetyl-CoA synthetase (ACS), alcohol dehydrogenase E (ADHE) and glutamate dehydrogenase (GDH) and the cyst wall protein (CWP1) gene in trophozoites, cysts and during the excystation process. Primers were designed to amplify mRNA fragments through quantitative reverse-transcriptase-polymerase-chain-reaction. In trophozoites, all transcripts of the enzymes studied were present. In cysts, three of the transcripts were detected: CWP1, GDH and ACS; but the relative levels of the mRNA of GDH and ACS were very different between trophozoites and cysts. During excystation, PFOR and ADHE transcripts appeared after the first induction phase, and the mRNAs of ACS and GDH increased throughout the process.
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PMID:Transcription of metabolic enzyme genes during the excystation of Giardia lamblia. 1466 85

Nicotinamide adenine dinucleotide (NAD+)-dependent protein deacetylases (sirtuins) and other enzymes that produce nicotinamide are integral to many cellular processes. Yet current activity measurements involve expensive and time-consuming assays. Here we present a spectroscopic assay that circumvents many issues of previous methods. This assay permits continuous product monitoring over time, allows determination of steady-state kinetic parameters, and is readily adaptable to high-throughput screening. The methodology uses an enzyme-coupled system in which nicotinamide is converted to nicotinic acid and ammonia by nicotinamidase. The ammonia is transferred to alpha-ketoglutarate via glutamate dehydrogenase, yielding glutamate and the oxidation of NAD(P)H to NAD(P)+, which is measured spectrophotometrically at 340 nm. Using this continuous assay with sirtuin-1 (Sirt1) and the ADP-ribosyl cyclase CD38, the resulting steady-state kinetic parameters are in excellent agreement with values obtained by other published methods. Importantly, this assay permitted determination of k(cat) and K(m) values with the native acetylated substrate acetyl-CoA synthetase-1; measurement of Sirt1, Sirt2, and Sirt3 activities from mammalian cell extracts; and determination of IC(50) values of various Sirt1 inhibitors. This assay is applicable to any nicotinamide-forming enzyme and will be an important tool to address many outstanding questions surrounding their regulation.
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PMID:A continuous microplate assay for sirtuins and nicotinamide-producing enzymes. 1961 66