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PubMedDate not supplied

[Thyroxine induction of aminotransferases in subcellular fractions of rat heart].

Administration of thyroxine toxic doses to rats results in a considerable increase in the alanine aminotransferase and aspartate aminotransferase activity in nuclear, mitochondrial and supernatant fractions of the rat heart. The hormone action is more pronounced in the mitochondrial fraction. A simultaneous administration of thyroxine and actinomycin D decreases the hormone effect in case of nuclear and supernatant enzymes. The enzymes of mitochondrial fractions do not change after actinomycin D injection. It is possible to suggest that in mitochondria there occurs a synthesis of some enzymes.

Alanine Transaminase↗

PubMed1997

[Glutamate oxalacetate and glutamate pyruvate aminotransferase activity in Streptomyces hygroscopicus 155 producing antibiotic complex].

Antibiotic activity, aminotransferase activity and composition of intracellular amino acids in low and high potent variants of Streptomyces hygroscopicus 155 were studied. The data of the study are indicative of some general regularities characteristic of amino acid metabolism in actinomycetes: an increased pool of the main aminodonor amino acids (alanine, asparaginic and glutaminic acids) and an increased activity of aminotransferases in the cultures of both the variants when grown in media with readily assimilable nitrogen sources.

Alanine↗

PubMed1998

A model for the nucleotide-binding domains of ABC transporters based on the large domain of aspartate aminotransferase.

ABC transporters are a large superfamily of integral membrane proteins involved inATP-dependent transport across biological membranes. Members of this superfamily play roles in a number of phenomena of biomedical interest, including cystic fibrosis (CFTR) and multidrug resistance (P-glycoprotein, MRP). Most ABC transporters are predicted to consist of four domains, two membrane-spanning domains and two cytoplasmic domains. The latter contain conserved nucleotide-binding motifs. Attempts to determine the structure of ABC transporters and of their separate domains are in progress but have not yet been successful. To aid structure determination and possibly learn more about the domain boundaries, we set out to model nucleotide-binding domains (NBDs) of ABC transporters based on a known structure. Previous attempts to predict the 3D structure of NBDs were based solely on sequence similarity with known nucleotide-binding folds. We have analyzed the sequences of a number of nucleotide-binding domains with the algorithm THREADER, developed by D.T. Jones, and a possible fold was found in the structure of aspartate aminotransferase. We present a model for the N-terminal NBD of CFTR, based on the large domain of the A chain of aspartate aminotransferase. The model is refined using multiple sequence alignment, secondary structure prediction, and 3D-1D profiles. Our model seems to be in good agreement with known properties of nucleotide-binding domains and has some appealing characteristics compared with the previous models.

ATP-Binding Cassette Transporters↗

PubMed1998

Study of serum alanine-aminotransferase levels in blood donors in Spain.

BACKGROUND AND OBJECTIVE: Serum alanine-aminotransferase (ALT) is being used as a surrogate test for preventing post-transfusion viral hepatitis. However, ALT elevation is influenced by many factors. We have studied ALT levels in 1,036 consecutive blood donors to determine their association with gender, obesity, and hepatitis virus infection markers. DESIGN AND METHODS: In each donation aspartate-aminotransferase (AST), lactate dehydrogenase (LDH) and gamma-glutamyl transferase (gamma GT) activity were also determined and body mass index (BMI) was calculated. RESULTS: Five hundred seventy-nine men and 457 women donated blood; ALT activity was 25.3 +/- 14.5 IU/L (mean +/- SD) for men and 16.3 +/- 7.9 IU/L for women (p < or = 0.0005). The upper normal value for men was 56 IU/L and 34 IU/L for women. On applying this value to the study group 4.8% of the men and 2% of the women had values greater than the cutoff. Among the men with increased ALT levels, 53.5% had a BMI > 27, 7.1% also had an increased level of GGT and 7.1% had increased levels of AST and LDH. None of them were HBsAg nor anti-HCV positive. Among the women with increased ALT, 33.3% had BMI > 27, 33.3% had increased levels of LDH and AST, and 11.1% were anti-HCV positive (only 1 donor). INTERPRETATION AND CONCLUSIONS: It seems clear that different cutoff values should be considered for men and women. Factors such as obesity, may account for more than 50% of the cases with increased ALT values, indicating the low specificity of the test.

Adolescent↗

PubMed1976

Aspartate aminotransferase activity in human serum. Factors to be considered in supplementation with pyridoxal 5'-phosphate in vitro.

The pyridoxal phosphate reactivation of the apo form of aspartate aminotransferase (EC 2.6.1.1) in human serum has been studied with "normal" and above-normal activity of this enzyme. The extent of the reactionation did not depend on the presence of the substrates, L-aspartate or 2-oxoglutarate. Reactivation was greatest with 110 mumol of added pyridoxal phsophate present per liter during a preinucation for 7 min in tris(hydroxymethyl)methylamine buffer wit;h serum volume fractions ranging from 0.017 to 0.267. In comparison with measurements prformed with no exogenous pyridoxal phosphate present, we found two potential sources of error when this cofactor was added: (a) reagent and sample blanks in the pyridoxal phosphate-supplemented system were two- to eightfold higher and (b) progress curves were nonlinear when L-aspartate rather than 2-oxoglutarate was used as the startin substrate. Aspartate aminotransferase measurement sith pyridoxal phosphate supplementation was slightly more precise than without.

Acute Disease↗

PubMedDate not supplied

[Serum and tissue aspartate and alanine aminotransferases activity of rats with vitamin A deficiency].

The activity of aspartate-(AST) and alanine (ALT) aminotransferases was studied in the tissues and blood serum of rats under conditions of A-avitaminosis. The activity of aminotransferases is established to increase in the blood serum and liver. In the small intestine mucose it drops sharply. The activity of ALT in the heart of the A-avitaminous animals lowers as well whereas AST does not change essentially its activity. Short fasting has no effect on the activity of the mentioned enzymes.

Alanine Transaminase↗

PubMed1989

Immunocytochemical localization of ornithine aminotransferase in human ocular tissues.

Gyrate atrophy of the choroid and retina is a rare inherited form chorioretinal degeneration caused by a deficiency of ornithine aminotransferase. We localized the enzyme in human ocular tissues using immunocytochemical procedures. Immunoreactivity was observed in the nonpigmented epithelium of the ciliary body and lens epithelium. In the retina, ganglion cells and some amacrine cells were immunoreactive. Pigmented granules made it difficult to identify immunoreactive products in the iris, pigmented epithelium of the ciliary body, choroid, and retinal pigment epithelium. Our findings suggested that ornithine aminotransferase plays an important role in ornithine metabolism in these oculartissues.

Eye↗

PubMed2006

Aminotransferase elevations in healthy adults receiving 4 grams of acetaminophen daily: a randomized controlled trial.

CONTEXT: During a clinical trial of a novel hydrocodone/acetaminophen combination, a high incidence of serum alanine aminotransferase (ALT) elevations was observed. OBJECTIVE: To characterize the incidence and magnitude of ALT elevations in healthy participants receiving 4 g of acetaminophen daily, either alone or in combination with selected opioids, as compared with participants treated with placebo. DESIGN, SETTING, AND PARTICIPANTS: A randomized, single-blind, placebo-controlled, 5-treatment, parallel-group, inpatient, diet-controlled (meals provided), longitudinal study of 145 healthy adults in 2 US inpatient clinical pharmacology units. INTERVENTION: Each participant received either placebo (n = 39), 1 of 3 acetaminophen/opioid combinations (n = 80), or acetaminophen alone (n = 26). Each active treatment included 4 g of acetaminophen daily, the maximum recommended daily dosage. The intended treatment duration was 14 days. Main Outcomes Serum liver chemistries and trough acetaminophen concentrations measured daily through 8 days, and at 1- or 2-day intervals thereafter. RESULTS: None of the 39 participants assigned to placebo had a maximum ALT of more than 3 times the upper limit of normal. In contrast, the incidence of maximum ALT of more than 3 times the upper limits of normal was 31% to 44% in the 4 treatment groups receiving acetaminophen, including those participants treated with acetaminophen alone. Compared with placebo, treatment with acetaminophen was associated with a markedly higher median maximum ALT (ratio of medians, 2.78; 95% confidence interval, 1.47-4.09; P<.001). Trough acetaminophen concentrations did not exceed therapeutic limits in any participant and, after active treatment was discontinued, often decreased to undetectable levels before ALT elevations resolved. CONCLUSIONS: Initiation of recurrent daily intake of 4 g of acetaminophen in healthy adults is associated with ALT elevations and concomitant treatment with opioids does not seem to increase this effect. History of acetaminophen ingestion should be considered in the differential diagnosis of serum aminotransferase elevations, even in the absence of measurable serum acetaminophen concentrations.

Acetaminophen↗

PubMed1997

Differences in binding of hepatic nuclear proteins from lean and obese rats to the 5'-upstream region of tyrosine aminotransferase.

The glucocorticoid effects on liver tyrosine aminotransferase mRNA levels have been studied in young, lean, and obese Zucker (fa/fa) rats and 5'-upstream regions of the tyrosine aminotransferase (TAT) gene have been used in gel retardation studies to investigate nuclear protein binding. Hepatic TAT mRNA levels were increased in obese fa/fa rats but were normalized seven days after adrenalectomy. Corticosterone replacement to adrenalectomized rats restored the increased levels of TAT mRNA in the obese animals. A 60-bp fragment of upstream TAT DNA (-2463 to -2403) was identified which showed higher levels of band shifting after incubation with hepatic nuclear proteins of obese rats compared with the proteins from lean animals. This differential level of gel retardation was substantially reduced by alkaline phosphatase treatment of nuclear proteins. Gel retardation was reduced when nuclear proteins were prepared from adrenalectomized obese rats, and increased with nuclear proteins from adrenalectomized rats replaced with corticosterone. DNA affinity chromatography and gel electrophoresis identified three proteins of approximately 58, 62, and 65 kDa in the DNA-protein complex. Increased amounts of these three proteins were purified from nuclei of obese rats. HNF3 alpha antibodies induced hypershift of the gel retardation pattern implicating HNF3 alpha as one of the proteins that binds to the 60 bp DNA fragment. The data support the hypothesis that decreased phosphorylation of nuclear proteins in obese rats is glucocorticoid-dependent and may contribute to the altered transcriptional activity of glucocorticoid-responsive genes.

Adrenalectomy↗

PubMed2005

Demonstration of kynurenine aminotransferases I and II and characterization of kynurenic acid synthesis in cultured cerebral cortical neurons.

The present study characterizes the synthesis of kynurenic acid (KYNA) from exogenously added kynurenine and its regulation by extrinsic factors, in cultured cerebral cortical neurons and, for comparison, in astrocytes incubated under identical conditions. The neuronal culture showed positive immunostaining for both kynurenic acid aminotransferase (KAT) isoforms I and II. Neurons synthesized KYNA at a rate about 2.3 times higher than astrocytes. Neuronal, but not astrocytic, KYNA synthesis was lowered approximately 30% by ionotropic glutamate receptor agonists [(R,S)-3-hydroxy-5-methoxyloxasole-4-propionic acid (AMPA; 100 microM) and N-methyl-D-aspartic acid (NMDA; 100 microM)] and depolarizing agents [KCl (50 mM) and 4-aminopyridine (4-AP; 10 microM)]. Neuronal and astrocytic synthesis alike were vulnerable to inhibition exerted by the aminotransferase inhibitor aminooxyacetic acid (AOAA), glutamate (IC50: 31 and 85 microM, respectively), substrates of the L-amino transport system [leucine (Leu); IC50: 19 and 42 microM, respectively] and 2-aminobicyclo[2,2,1]heptane-2-carboxylic acid (BCH; IC50: 19 and 28 microM, respectively). Glutamine (Gln), which is a metabolic precursor of glutamate in astrocytes and L-system substrate in both cell types, inhibited KYNA synthesis both in neurons and in astrocytes (IC50: 268 and 318 microM, respectively). alpha-Ketoisocaproic acid (KIC), a Leu transamination product that is produced mainly in astrocytes and shuttled to neurons to modulate intraneuronal concentration of glutamate, stimulated KYNA synthesis in neurons but did not affect the synthesis in astrocytes. In conclusion, this study is the first to demonstrate active, regulation-prone KYNA synthesis in neurons.

Animals↗

PubMed1983

Activities of arginase, transamidinase, and ornithine aminotransferase in glia, neurons, and synaptosomes.

The regional, cellular, and subcellular distribution of some enzymes of the urea cycle in brain is not clearly known. Glia, neurons, and synaptosomes have been prepared from rat cerebral cortex and arginase (EC 3.5.3.1), transamidinase (EC 2.1.4.1), and ornithine aminotransferase (EC 2.6.1.13) have been estimated in order to understand the metabolic and functional role of these enzymes. It has been observed that arginase is predominantly localized in synaptosomes and neurons. The ornithine aminotransferase was found to be high in glial cells and very high in synaptosomes (higher than arginase). Transamidinase was mostly localized in glial cells. The implication of these results has been discussed in relation to a possible role of ornithine acting as a precursor of glutamate in glutametargic nerve endings and its possible participation in the glutamate-glutamine cycle.

Acyltransferases↗

PubMed1992

Purification and characterization of an inducible L-lysine: 2-oxoglutarate 6-aminotransferase from Candida utilis.

L-Lysine:2-oxoglutarate 6-aminotransferase (EC 2.1.6.36) was purified 202-fold from the yeast Candida utilis. The subunit Mr estimated by sodium dodecyl sulfate polyacrylamide gel electrophoresis was 40 kDa. The Mr of the native enzyme was estimated to be 83 kDa by gel filtration, suggesting a dimeric structure. The enzyme exhibits absorption maxima at 280, 340 and 420 nm, and binds 2 mol pyridoxal-5-phosphate/mol of the native enzyme. The aminotransferase has a maximum activity at pH 8.5 and at 4 degrees C. 2-Oxoglutarate is the best amino acceptor with L-lysine as amino donor. Lower activity is observed with oxaloacetate (38%), pyruvate (19%) and 2-oxoadipate (7%) as acceptor or with L-thialysine (13%) as donor. The Km values are 2.5 mM for L-lysine, 3.8 mM for 2-oxoglutarate and 0.015 mM for pyridoxal-5-phosphate. The enzyme activity is induced in cells grown in the presence of L-lysine.

Candida↗

PubMed2004

Alanine : glyoxylate aminotransferase of Saccharomyces cerevisiae-encoding gene AGX1 and metabolic significance.

Alanine : glyoxylate aminotransferase is one of three different enzymes used for glycine synthesis in Saccharomyces cerevisiae. The open reading frame YFL030w (named AGX1 in the following), encoding this enzyme, was identified by comparing enzyme specific activities in knockout strains. While 100% activity was detectable in the parental strain, 2% was found in a YFL030w::kanMX4 strain. The ORF found at that locus was suspected to encode alanine : glyoxylate aminotransferase because its predicted amino acid sequence showed 23% identity to the human homologue. Since the YFL030w::kanMX4 strain showed no glycine auxtrophic phenotype, AGX1 was replaced by KanMX4 in a Delta GLY1 Delta SHM1 Delta SHM2 background. These background mutations, which cause inactivation of threonine aldolase, mitochondrial and cytosolic serine hydroxymethyltransferase, respectively, lead to a conditional glycine auxotrophy. This means that growth is not possible on glucose but on ethanol as the sole carbon source. Additional disruption of AGX1 revealed a complete glycine auxotrophy. Complementation was observed by transformation with a plasmid-encoded AGX1.

Alanine↗

PubMed1993

Characterization and sequence analysis of rat serine:pyruvate/alanine:glyoxylate aminotransferase gene.

We have reported the isolation of genomic clones encoding serine:pyruvate aminotransferase (SPT; also named alanine:glyoxylate aminotransferase, AGT) (T. Oda, T. Funai, and A. Ichiyama, 1990, J. Biol. Chem. 265: 7513-7519). These clones contained the entire SPT/AGT gene of 10 kb. In this work, we characterized this gene. The SPT/AGT gene consists of 11 exons, and the exon-intron boundaries have typical splice donor and acceptor sequences. Determination of the nucleotide sequence up to -1.25 kb from the transcription initiation site revealed the presence of many putative cis elements, some of which may explain the transcriptional regulation of the SPT/AGT gene by glucagon and glucocorticoid. The nucleotide sequence around the 5' flanking region of the rat SPT/AGT gene and the whole gene organization were compared with those of the human SPT/AGT gene. No obvious similarities were observed in the 5' flanking region up to -1.25 kb from the initiation site of the gene, but exons 2 to 10 of the rat and human genes have identical sizes and show high similarities.

Alanine Transaminase↗

PubMed1996

Kynurenine aminotransferases in the rat. Localization and characterization.

Kynurenine-2-oxoglutarate aminotransferase (kynurenine specific, designated here KAT-II) and kynurenine pyruvate aminotransferase (designated here KAT-I) activities were detected in the kidney using 2 microM kynurenine. The major activities were performed by KAT-II and the contributi-n of KAT-I is about 1/15. KAT-I activity was detected in all organs tested. The liver showed the highest KAT-I activity, however, the highest activity of glutamine transaminase-K (GTK) was detected in the kidney. KAT-I activity was well corresponded with GTK activity in all organs except liver. KAT-I or GTK activity of crude extract didn't inhibited by addition of glutamine either kynurenine. KAT-I or GTK activity of purified preparation, however, inhibited strongly addition of glutamine either kynurenine. KAT-I and GTK showed different pH optimum profile, but purified and crude preparation of those were similar. Phenylpyruvate or 2-oxo-4-methiolbutyrate reduced the inhibition of purified KAT-I activity by glutamine using 2 microM kynurenine. Phenylpyruvate changed the Km value for kynurenine and Vmax, suggesting conformational change of the enzyme.

Amino Acids↗

PubMed1999

Liver and kidney kynurenine aminotransferase activity in different strains of rats.

Variations in liver and kidney kynurenine aminotransferase (KAT) activity in Pittsburg-Yoshida, Brown-Norway, albino Wistar, Sprague-Dawley, Long Evans and heterozygous Gunn rats were studied. In liver, values of KAT specific activity, expressed as mumoles of kynurenic acid formed per hour per mg of protein, were different in the groups of Brown-Norway and Pittsburg-Yoshida rats versus Long Evans and Sprague-Dawley rats. The activity expressed as mumoles of kynurenic acid per g of fresh liver showed other differences, being significantly higher in Gunn with respect to other strains of rats and lower in Pittsburg-Yoshida and Brown-Norway rats. In addition, KAT activity was significantly lower in Pittsburg-Yoshida than in Brown-Norway rats. In kidney, the specific activity of kynurenine aminotransferase showed significant differences in the values of Sprague-Dawley and Long Evans rats versus the other strains. The activity expressed per g of fresh tissue was significantly higher in Wistar, Sprague-Dawley, Long Evans and Gunn than in Pittsburg-Yoshida and Brown-Norway rats. No significant differences were found in values between hyperlipidemic Pittsburg-Yoshida and their control Brown-Norway rats. These results high-light the importance of considering various rat strains when inbred animal experimental models are used.

Animals↗

PubMed1981

Induction of tyrosine aminotransferase by pyridoxine in Drosophila hydei.

Salivary glands incubated in various concentrations of pyridoxine (Vitamin B6) show increasing tyrosine aminotransferase (TAT) activity at concentrations up to 10(-5) M and then decreasing activity up to 10(-2) M but in all cases the activity is greater than that of the controls. This increase in activity is demonstrable for up to 6 h, the longest period tested, and is dependent on the synthesis of new mRNA. A similar increase in TAT activity is observed in salivary glands subjected to heat shock. Antibodies prepared against purified tyrosine aminotransferase precipitate a peptide of the same molecular weight (40 KD) as that induced by pyridoxine.

Animals↗

PubMed1984

Alanine aminotransferase in the rat nervous system during the postnatal development referring to the glutamate transmitter metabolism.

Alanine aminotransferase has been studied in various nervous tissues during the postnatal development of the rat. At birth the enzyme activity was low and showed similar levels in all tissues studied. In the hippocampal formation and in the cerebellum which are supposed to be endowed with glutamatergic structures, the enzyme activity increased significantly during the postnatal development. These results contrast markedly with dorsal root ganglia and superior cervical ganglia, in which glutamatergic transmission processes are obviously absent. In these peripheral ganglia the time course of the enzyme activity persisted on a very low level after birth. The participation of alanine aminotransferase in forming of transmitter glutamate is discussed.

Alanine Transaminase↗