Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P17174 (aspartate aminotransferase)
 14,872 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The isolated perfused rat kidney was shown to synthesize serine from aspartate or glutamate, both of which are also precursors of glucose. The major products of aspartate metabolism were ammonia, serine, glutamate, glucose, glutamine and CO2. Perfusion of kidneys with aspartate in the presence of amino-oxyacetate resulted in a near-complete inhibition of aspartate metabolism, illustrating the essential role of aspartate aminotransferase in the metabolism of this substrate. Radioactivity from 14C-labelled aspartate and from 14C-labelled glycerol was incorporated into serine and glucose. Production of both glucose and serine from aspartate was suppressed in the presence of 3-mercaptopicolinic acid. These data provide evidence for the operation of the phosphorylated and/or non-phosphorylated pathway for serine production to the presence of 3-mercaptopicolinic acid. This is explained by simultaneous glycolysis. The rate of glucose production, but not that of serine, was greater in kidneys perfused with glutamate or with aspartate plus glycerol than the rates obtained by perfusion with aspartate alone. These data are taken to suggest that serine synthesis occurred at a near-maximal rate, and that the capacity of the kidney for serine synthesis from glucose precursors is lower than that for glucose synthesis.
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PMID:Serine synthesis by an isolated perfused rat kidney preparation. 286 20

Mitochondria from rat white adipose tissue were prepared, exhibiting good respiratory control and P/O ratios. They would not oxidize NADH unless NNN'N'-tetramethyl-p-phenylenediamine was added as a carrier of reducing equivalents. These mitochondria were found to oxidize neither l-glycerol 3-phosphate nor l-glutamate plus l-malate at significant rates. The activity of aspartate aminotransferase in these mitochondria was found to be low compared with that found in rat liver mitochondria. As a consequence of this, the adipose-tissue mitochondria exhibited very low rates of cytoplasmic NADH oxidation in a reconstituted Borst (1962) cycle compared with liver mitochondria.
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PMID:Transport of reduced nicotinamide-adenine dinucleotide into mitochondria of rat white adipose tissue. 431 14

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

1. Incubation of isolated liver cells in a medium containing bicarbonate raises malate concentrations almost sixfold compared with values obtained in a bicarbonate-free phosphate medium. The malate concentration of about 0.3mm in bicarbonate medium is of the same order as the K(m) for malate dehydrogenase. 2. The utilization of ethanol, glyercol and sorbitol was increased by 20-35% in bicarbonate medium. 3. Fluoromalate, a specific inhibitor of malate dehydrogenase and the malate carrier, inhibited or ethanol oxidation by 23%, glycerol uptake by 20% and sorbitol uptake by 42% in bicarbonate medium, but had a much smaller inhibitory action in phosphate medium. In consequence fluoromalate almost abolished the stimulatory effects of bicarbonate on substrate utilization. 4. Difluoro-oxaloacetate, a specific inhibitor of aspartate aminotransferase, had about one-half the inhibitory activity of fluoromalate. The two inhibitors in combination were less effective than fluoromalate by itself. 5. It is concluded that bicarbonate stimulates the utilization of reduced substrates, which are oxidized in the cytoplasmic compartment of the liver cell, by increasing the activity of rate-limiting malate dehydrogenase-dependent intercompartmental hydrogen shuttles. Both malate-oxaloacetate and malate-aspartate systems are involved in these hydrogen-translocation processes.
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PMID:Effects of bicarbonate on intercompartmental reducing-equivalent translocation in isolated parenchymal cells from rat liver. 444 23

The effects of 1-naphthyl-N-methylcarbamate (carbaryl) upon glucose production from several precursors (lactate, glycerol, alanine, fructose and pyruvate) and on activities of gluconeogenic enzymes (glucose-6-phosphatase, lactate dehydrogenase and aspartate aminotransferase) in isolated rat hepatocytes was studied. The results show that carbaryl inhibits lactate-gluconeogenesis at all concentrations of substrate studied. Gluconeogenesis from 10 mM fructose or 10 mM pyruvate or 10 mM alanine is also inhibited by carbaryl 1 mM. However, glycerol-gluconeogenesis is unaffected. Concentrations of carbaryl at 0.01 and 0.1 mM did not significantly modify lactic dehydrogenase activity, but at 1.0 mM this activity was reduced by 38% in relation to the dimethylsulphoxide-treated group. The synthetic activity of glucose-6-phosphatase is enhanced by carbaryl, but the increase is only significant for 1 mM carbaryl. In the study of aspartate aminotransferase activities two fractions, cytoplasmic and mitochondrial, are differentiated; and, it is observed that both fractions are inhibited by 0.1 and 1.0 mM carbaryl. The results indicate that carbaryl produces major decreases of the glucose production by hepatic cells, and suggest that the carbaryl-induced hyperglycemia in the fasted animal would be due to deficiencies in the peripheral utilization of the glucose.
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PMID:The interaction of carbaryl with the metabolism of isolated hepatocytes: II. Effect on gluconeogenesis. 609 5

Venous blood samples and middle gluteal muscle biopsies were obtained from 21 horses taking part in 100 km or 50 km endurance rides. Group A consisted of seven horses competing over 100 km (four horses completed the ride). Group B consisted of the six horses that were among the 10 best over 50 km while the other eight horses of Group C completed 50 km at a slower speed. Blood lactate, glycerol and creatine kinase increased in all groups while aspartate aminotransferase levels were higher only in Group A. No changes was found in blood glucose in Groups B and C while horses in Group A had lower levels after the ride. Neither fibre composition, fibre areas nor enzyme activities differed between the groups. Intramuscular glycogen content was similar before the ride in all groups. After the ride glycogen had decreased only half as much in Group C as compared to Groups A and B. Group C had a higher intramuscular triglyceride content at rest than Group B. The greatest decrease in triglyceride content after the ride was found in Group C. In Group A and B many Type I, IIA and IIB fibres were glycogen depleted after the ride while in Group C mainly Type I and some Type IIA fibres were depleted. The results of this study show that intramuscular carbohydrate and lipid stores are both important fuels during endurance rides.
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PMID:Fibre types, enzyme activities and substrate utilisation in skeletal muscles of horses competing in endurance rides. 673 85

The effect of different glycerol concentrations (0 to 5.3 per cent) on motility, viability and aspartate aminotransferase (AST) release of stallion spermatozoa was studied before and after deep-freezing. Addition of glycerol to a TRIS-fructose-egg yolk diluent used to extend stallion semen had no effect on motility and viability of spermatozoa and it did not increase AST release. Inclusion of glycerol in the extender only partially preserved the motility and viability of stallion semen during deep-freezing. A fertility trial revealed that concentrating stallion semen by centrifugation, followed by addition of the extender containing 7.5 per cent glycerol, had little effect on fertility and a 70 per cent conception rate was obtained in 10 mares after inseminations during one service period. Freezing and thawing horse spermatozoa, even in the presence of 7.5 per cent glycerol, significantly decreased the fertilisation rate.
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PMID:Effect of glycerol on motility, viability, extracellular aspartate aminotransferase release and fertility of stallion semen before and after freezing. 729 48

In a comparative study, the differences between the values measured for 26 blood and serum components in both winter and summer were determined in 78 healthy subjects. Comparable conditions during the preparation of test persons, sampling, processing of specimens, and measurement were strictly observed. The term "season" is defined more precisely by meterological data. In the summer season, significantly higher values were found for leukocytes (9%), lactate dehydrogenase and MCHC (7% each), creatinine (7%, in women only), and MCH (1%) whereas significantly lower values were exhibited by aspartate aminotransferase (18%), alanine aminotransferase (14%), alkaline phosphatase (11%), glucose and packed cell volume (7% each), MCV (6%), total protein (2%), erythrocytes, albumin, sodium and chloride (1% each). These partly considerable alterations should be taken into account in the establishment of reference values and evaluation of laboratory findings (above all, when intraindividual comparison is involved). There were no significant alterations of the following parameters: hemoglobin, gamma-glutamyl transferase, urea, uric acid, creatinine (men only), bilirubin, cholesterol, total glycerol, potassium, calcium, and inorganic phosphate. In another series of experiments involving 32 test persons, the influence of different ambient temperatures during blood sampling on the above mentioned blood components was studied. Within the 18-30 degrees C range, no significant alterations were detected.
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PMID:[Seasonal variation of blood components important for diagnosis (author's transl)]. 744 84

The influence of enhancing the supply of hydrogen donors on respiratory rates, NAD(P)H fluorescence, and membrane potential was investigated. Addition of 5 mM malate to mitochondria during oxidation of 10 mM isocitrate, oxoglutarate, succinate, proline, or glycerol-3-phosphate under steady-state conditions resulted in an inhibition of respiration, coincident with a decrease in both transmembrane electrical potential and percentage reduction of NAD(P). Half-maximum inhibition of NAD(P) reduction in the resting state of 10 mM isocitrate respiration was reached at 10 mM malate. This inhibition was concluded to be due to oxaloacetate formed immediately from malate by succinate dehydrogenase. Addition of 5 mM isocitrate caused higher respiratory rates, accompanied by an increase in both delta psi and percentage of NAD(P) reduction, in mitochondria oxidizing 10 mM oxoglutarate, glutamate, proline, hydroxybutyrate, glycerol-3-phosphate, or 0.025 mM palmitoyl carnitine. The half-maximum increase in percentage NAD(P) reduction with 10 mM 2-oxoglutarate as primary substrate was found at 0.24 mM isocitrate. Within the citric acid cycle, succinate dehydrogenase and NAD-isocitrate dehydrogenase play an important role in changes in the rate of NADH formation. Therefore, they participate in flux control. Furthermore, mitochondrial aspartate aminotransferase and oxidoreductases of the beta-oxidation pathway of fatty acids are additionally involved in adjusting the rate of NADH formation.
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PMID:Contribution to control of mitochondrial oxidative phosphorylation by supplement of reducing equivalents. 791 69

In islets from adult rats injected with streptozotocin during the neonatal period, both a nonmetabolized analog of L-leucine and 3-phenylpyruvate augmented 14CO2 output from islets either prelabeled with L-[U-14C]glutamine or exposed to D-[2-14C]glucose and D-[6-14C]glucose, in a manner qualitatively comparable to that found in islets from control rats. The islets of diabetic rats differed, however, from those of control rats by their unresponsiveness to both the L-leucine analog and a high concentration of D-glucose in terms of increasing 3HOH generation from [2-3H]glycerol, an impaired sparing action of the hexose upon 14CO2 output from islets prelabeled with [U-14C]palmitate, and, most importantly, by a decreased rate of D-[2-14C]glucose and D-[6-14C]glucose oxidation when either incubated at a high concentration of the hexose (16.7 mM) or stimulated by nonglucidic nutrient secretagogues at a low concentration of D-glucose (2.8 mM). In islet homogenates, the activity of glyceraldehyde phosphate dehydrogenase, glutamate decarboxylase, and NADP-malate dehydrogenase was lower in diabetic than control islets. Such was not the case for glutamate-alanine transaminase, glutamate-aspartate transaminase, or glutamate dehydrogenase. The neonatal injection of streptozotocin thus affected, in the adult rats, the activity of several islet enzymes. Nevertheless, the metabolic data suggest that an impaired circulation in the glycerol phosphate shuttle, as observed in response to stimulation of the islets by either a high concentration of D-glucose or nonglucidic nutrient secretagogues, represents an essential determinant of the preferential impairment of glucose-induced insulin release in this model of non-insulin-dependent diabetes.
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PMID:Metabolic response to nonglucidic nutrient secretagogues and enzymatic activities in pancreatic islets of adult rats after neonatal streptozotocin administration. 848 60


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