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:2.6.1.1 (aspartate aminotransferase)
21,665 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effects of recombinant human interleukin-1 beta (rhIL-1 beta) on various serum constituents were studied following subcutaneous injection (12.5 or 125 micrograms/kg) in female Wistar rats. Protein electrophoresis and the determination of the serum concentrations of carboxypeptidase N (CPN), aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, aldolase, total proteins, iron, urea, creatinine, and several amino acids were performed 12, 24, and 72 hr after injection. With both doses of rhIL-1 beta, iron, albumin, CPN, and lysine were significantly decreased whereas alpha 2-globulin, urea, and creatinine were significantly increased 12 hr after administration. Iron and CPN were still low after 24 hr but returned to normal levels after 72 hr. With the higher dose of rhIL-1 beta, only alanine and phenylalanine levels were increased after 12 and 72 hr, taurine after 12 hr, and methionine after 24 hr. There were no biochemical or histological signs of hepatotoxicity. The findings indicate that rhIL-1 beta produces a reversible alteration of various biochemical plasma constituents without any apparent signs of cytotoxicity. Moreover, the decrease in CPN observed may influence the degradation of inflammatory peptides.
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PMID:Recombinant human interleukin-1 beta decreases serum carboxypeptidase N and modifies serum amino acid concentrations in rats. 278 29

Recently we reported that the contractile agonist angiotensin II induces hypertrophy, not hyperplasia, in cultured rat aortic smooth muscle cells (Geisterfer AAT, Peach MJ, Owens GK: Angiotensin II induces hypertrophy, not hyperplasia, of cultured rat aortic smooth muscle cells. Circ Res 1988;62:749-756). We have further explored the hypothesis that contractile agonists are important regulators of smooth muscle cell growth by examining the effects of another contractile agonist, arginine vasopressin, on growth of cultured rat aortic smooth muscle cells. Autoradiographic analysis as well as cell number determinations showed that arginine vasopressin (1 microM) did not stimulate proliferation in cells made quiescent in a defined serum-free media nor did it augment proliferation in 0.4% fetal bovine serum. However, flow cytometric analysis of cellular protein content demonstrated that arginine vasopressin (1 microM) did induce cellular hypertrophy in quiescent cultures after 4 days of treatment, increasing smooth muscle cell protein content by 35% as compared with vehicle-treated controls. The increase in protein content showed a concentration dependence. Cellular hypertrophy was accompanied by an increase in [35S]methionine incorporation, which was elevated 45% by 24 hours. Both the increase in [35S]methionine incorporation and the increase in protein content could be prevented by the specific arginine vasopressin receptor antagonist. [1-beta-mercapto-beta,beta-cyclopentamethylene propionic acid), 2-(O-methyl)tyrosine] arginine vasopressin. An increase in [35S]methionine incorporation was observed between 12 and 24 hours after treatment of quiescent smooth muscle cells for only 5 minutes with arginine vasopressin (1 microM). Arginine vasopressin-induced increases in [35S]methionine incorporation was increased within 6 hours after treatment. These studies show that arginine vasopressin, like angiotensin II, induces hypertrophy but not hyperplasia of cultured rat aortic smooth muscle cells.
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PMID:Arginine vasopressin-induced hypertrophy of cultured rat aortic smooth muscle cells. 279 15

The mechanism of expression of the overlapping genes that encode the alpha and beta subunits of aspartokinase II of Bacillus subtilis was studied by specific mutagenesis of the cloned coding sequence. Escherichia coli or B. subtilis VB31 (aspartokinase II-deficient), transformed with plasmids carrying either a deletion of the translation start site and about one-half of the coding region for the larger alpha subunit or a frameshift mutation early in the alpha subunit coding region, produced the smaller beta subunit in the absence of alpha subunit synthesis, indicating that beta subunit is not derived from alpha subunit and that its synthesis does not depend on the alpha subunit translation initiation site. The beta subunit translation start site was identified by oligonucleotide-directed mutagenesis of the putative translation start codon. Modification of the nucleotide sequence encoding methionine residue 247 of the alpha subunit from ATG to either TTA or AAT (but not GTG) abolished beta subunit synthesis but had no effect on the production of alpha subunit. This observation is consistent with peptide chain initiation by N-formylmethionine, which specifically requires an ATG or GTG sequence, and indicates that translation of the beta subunit starts at a site corresponding to Met247 of the alpha subunit. Initial studies on the function of the aspartokinase II subunits, using E. coli as a heterologous host, showed that beta subunit was not essential for the expression of the catalytic function of aspartokinase, measured in vitro and in vivo, nor for its allosteric regulation by L-lysine. Whether the beta subunit has a function specific to B. subtilis needs to be explored in a homologous expression system.
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PMID:Mechanism of expression of the overlapping genes of Bacillus subtilis aspartokinase II. 283 91

Both the precursor and the mature form of chicken mitochondrial aspartate aminotransferase were synthesized in Escherichia coli. The precursor was found to sediment quantitatively together with insoluble cell material. In contrast, mature mitochondrial aspartate aminotransferase could be readily extracted from the cells and was indistinguishable from the enzyme isolated from chicken heart in all respects tested: specific activity 230 units mg-1; Mr 2 X 45,000; pI greater than 9; NH2-terminal sequence SSWWSHVEMG, the initiator methionine having been removed by the bacteria. Thus, the polypeptide chain representing mature mitochondrial aspartate aminotransferase is an autonomous folding unit which attains its functional spatial structure independently of the presence of the prepiece, trans-membrane passage, and proteolytic processing.
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PMID:Expression of cDNAs encoding the precursor and the mature form of chicken mitochondrial aspartate aminotransferase in Escherichia coli. 330 9

An experiment was conducted with 576 female Cobb feather-sexed chicks to study the influence of methionine (MET) and selected nutrient (SN) supplementation on the performance of chicks fed high Cu levels. Day-old chicks were allotted randomly to pens for the 22-day experiment. A 3 X 2 X 2 factorial arrangement of treatments was used which included Cu at 0, 400, and 800 mg/kg, MET at 0 and .4%, and SN at 0 and 20%. A significant (P less than .001) Cu X MET X SN interaction was found for gain. Supplemental MET reversed the growth depression observed in birds fed 400 but not 800 mg/kg Cu. Additions of 400 and 800 mg/kg Cu to the basal diet depressed (P less than .001) feed consumption by 8.6 and 19.4%, respectively. Hepatic Cu concentrations increased linearly (P less than .001) with increasing dietary Cu and were not influenced (P greater than .10) by supplemental MET or SN. Liver weights increased linearly (P less than .001) with increasing dietary Cu and were higher (P less than .05) for chicks on diets supplemented with SN, but lower (P less than .05) for those with diets supplemented with MET. The interaction of MET X SN was significant (P less than .001) for serum Cu; chicks supplemented with SN in conjunction with MET had the lowest (P less than .05) serum Cu concentrations. Serum glutamic-oxaloacetic transaminase (SGOT) activity was not influenced (P greater than .10) by dietary Cu, but SN supplementation resulted in a 10% elevation (P less than .001) in SGOT activity.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Interaction of dietary nutrient concentration and supplemental copper on chick performance and tissue copper concentrations. 368 58

Mitochondrial aspartate aminotransferase is synthesized on free polysomes as a higher molecular weight precursor (Sonderegger, P., Jaussi, R., Christen, P., and Gehring, H. (1982) J. Biol. Chem. 257, 3339-3345). The present study examines whether the coenzyme pyridoxal phosphate or pyridoxamine phosphate is required for the uptake of the precursor into mitochondria. Chicken embryo fibroblasts were cultured in medium prepared with and without pyridoxal. In cells grown in the presence of pyridoxal only holoform of aspartate aminotransferase and no apoenzyme was detected. Cells cultured under pyridoxal deficiency contained about 30% of apoenzyme in secondary cultures. All of this apoform was identified as mitochondrial isoenzyme. In order to differentiate whether this apoenzyme corresponded to newly synthesized protein or originated from pre-existing holoenzyme, double isotope-labeling experiments were performed. Secondary cultures of chicken embryo fibroblasts grown under pyridoxal depletion were labeled with [3H]methionine, and then pulsed with [35S]methionine. In another series of experiments, the 3H-labeled cells were pulsed with [35S]methionine in the presence of the protonophore carbonyl cyanide m-chlorophenylhydrazone in order to accumulate the precursor. Subsequently, the accumulated precursor was chased into the mitochondria by addition of the carbonyl cyanide m-chlorophenylhydrazone antagonist cysteamine. The holo- and apoenzyme from the ultrasonic extract of the double-labeled cells were separated by affinity chromatography on a phosphopyridoxyl-AH-Sepharose column, immunoprecipitated, and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography. Under both experimental conditions, the 3H/35S ratio of the apoenzyme was less than half of that of the holoenzyme. Therefore, the apoenzyme and not the holoenzyme is the first product of the precursor in the mitochondria. Apparently, the precursor of mitochondrial aspartate aminotransferase is transported into mitochondria as apoprotein and is processed there independently of the coenzyme.
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PMID:The precursor of mitochondrial aspartate aminotransferase is translocated into mitochondria as apoprotein. 373 49

The purpose of this study was to determine whether a vitamin B6 deficiency affects the utilization of 2-hydroxy-4-(methylthio) butanoic acid (HMB), an analogue of methionine. The basal diet used for this purpose was based on peas, peanut meal, and glucose monohydrate and was low in both methionine and pyridoxine. Supplemental pyridoxine hydrochloride and L-methionine or HMB resulted in significant increases in growth rate and efficiency of feed utilization; supplemental pyridoxine also produced significant increases in the activity of glutamic-oxaloacetic transaminase (PGOT, EC 2.6.1.1.) in plasma. There was no discernible effect of change in vitamin B6 status on the utilization of HMB as compared with L-methionine.
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PMID:The lack of effect of a pyridoxine deficiency on the utilization of the hydroxyl analogue of methionine by the chick. 373 8

A two-stage surgical occlusion of the portal vein was employed to produce hyperammonaemia in the rat. The procedure resulted in a significant rise of arterial blood ammonia level from 70 . 5 +/- 6 . 5 mumol/l (mean +/- SEM, n = 10) to 214 . 0 +/- 37 . 7 mumol/l and in a rise of venous blood ammonia from 65 . 0 +/- 9 . 4 mumol/l to 122 . 2 +/- 7 . 4 mumol/l during the first day following the complete vein occlusion. A marked increase of the arteriovenous difference of ammonia concentration from virtually zero in sham-operated controls to 72 +/- 9 (n = 8) mumol/l in rats 1 day after the surgical manipulation suggested uptake of ammonia by skeletal muscle. Rat muscle glutamine synthetase activity increased from 0 . 46 +/- 0 . 06 u/mg (n = 7) in controls to 2 . 7 +/- 0 . 3 u/mg (n = 7) on the fourth day following portal vein ligation, and muscle branched chain amino acids aminotransferase increased from 0 . 2 +/- 0 . 05 u/mg in controls to 0 . 96 +/- 0 . 1 u/mg (n = 7) during the first day of ligation. Glutamine dehydrogenase and aspartate aminotransferase activities were not affected by the surgical procedure. These observations suggest that ammonia trapping in skeletal muscle is coupled to glutamine formation via amination of glutamic acid. This conclusion was further supported by the finding that ammonia uptake correlated (r = 0 . 92) with enhanced release of glutamine from muscle and that treatment with methionine sulfoximine, a potent inhibitor of glutamine synthetase, changed the arteriovenous difference of glutamine from -0 . 92 +/- 0 . 01 mmol/l in ligated animals (net release) to +0 . 12 +/- 0 . 01 mmol/l (net uptake) in ligated and inhibitor-treated animals. Similarly, the inhibitor also abolished the arterio-venous difference of ammonia. Thus, the animal model of hyperammonaemia and the muscle enzyme assays reveal that skeletal muscle is involved in the regulation of blood ammonia level by conversion of ammonia, via glutamic acid, to glutamine.
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PMID:Ammonia uptake by skeletal muscle in the hyperammonaemic rat. 612 77

Cytoskeleton inhibitors were tested in chicken embryo fibroblast cultures for possible effects on the import of the precursor of mitochondrial aspartate aminotransferase into mitochondria. Vinblastine (50 microM) increased the steady-state pool of the precursor 2.5-fold in pulse experiments with [35S]methionine. If the precursor was accumulated during a pulse in the presence of the uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP) and then chased under diluting CCCP, vinblastine (50 microM) prolonged the half-life of the precursor from 0.5 min in the control to 3 min. Other cytoskeleton inhibitors, i.e. vincristine (25 to 150 microM), colchicine (50 microM), nocodazole (50 microM), podophyllotoxin (50 microM), taxol (45 microM), cytochalasin D (20 microM) and phalloidin (25 microM) did not show this effect. The observed inhibition by vinblastine does not seem to relate to its action on microtubuli.
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PMID:Vinblastine inhibits the maturation of the precursor of mitochondrial aspartate aminotransferase. Vincristine and six other cytoskeleton inhibitors do not show this effect. 613 15

The enzymes of glutamate metabolism were estimated in astrocytes isolated from brains of normal rats and those injected with the potent convulsant, methionine sulfoximine (MSO), which inhibits glutamine synthetase and induces Alzheimer type II astrocytosis. The wet weight, dry weight; contents of DNA, RNA, protein and the activities of glutamate dehydrogenase and aspartate aminotransferase were elevated following MSO administration. The metabolic effects of MSO were found to be different from those of ammonia wherein a fall in the activity of glutamate dehydrogenase and an increase in the activity of glutamine synthetase was noticed. Based on these results it is suggested that there might be an inverse relationship in the functioning of these two enzymes. Such a relationship would help in preventing the depletion of energy pools in a given cellular compartment during ammonia detoxification.
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PMID:Effects of methionine sulfoximine on the enzymes of glutamate metabolism in isolated astrocytes of rat brain. 614 Sep 23


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