SEARCH · PubMed Health

Results for “ASPARTATE AMINOTRANSFERASE”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 595 records · Page 33Linked to original sources

PubMedDate not supplied

[Aspartate aminotransferase metabolism in muscles during physical exercise].

It is established that the concentration of cytosolic aspartate aminotransferase decreases the first day after intensive physical exercises due to the intensification of the degradation processes, the decrease in the synthesis rate and the enzyme entry into the blood vessel. The enzyme content is normalized by the 24th hour of rest and then the supercompensatory phase takes place: the enzyme biosynthesis increases and its degradation decreases to a greater extent.

Animals↗

PubMed1988

Liver aspartate aminotransferase activity as a power function of body weight.

Total liver enzyme activity (E) for aspartate aminotransferase (ASAT; EC 2.6.1.1) per gram body weight (W) decreases in six species as body weight increases from mice to cattle according to the equation E/W 0.85 = c, where c is a constant. The 0.85 power of body weight thereby provides a reference standard for the direct arithmetic comparison of liver ASAT activities in six species with different body weights. The use of W 0.85 should provide a tool in clinical studies in which data from experimental animals must be related to humans, e.g., in establishing the relationship between drug dosage (or toxicity) and body weight.

Adult↗

PubMed1999

The ratio of aspartate aminotransferase to alanine aminotransferase: potential value in differentiating nonalcoholic steatohepatitis from alcoholic liver disease.

OBJECTIVE: The ratio of aspartate aminotransferase (AST) to alanine aminotransferase (ALT) is often greater than 2:1 in alcoholic hepatitis. The purpose of this study was to determine whether this ratio may be used to distinguish nonalcoholic steatohepatitis (NASH) from alcoholic liver disease. METHODS: Patients with NASH were matched with controls with alcoholic liver disease based on age, gender, and date of diagnosis. The diagnosis of alcoholic liver disease was based on exclusion of other causes and a significant history of alcohol consumption. The diagnosis of nonalcoholic steatohepatitis was based on exclusion of other causes of liver disease and a liver biopsy showing > 10% steatosis and inflammation. The two sided Student t test was used for statistical analysis. RESULTS: From 1990 to 1996, 70 patients with NASH were matched with 70 subjects with alcoholic liver disease. Patients with NASH had a mean AST to ALT ratio of 0.9 (range 0.3-2.8, median 0.7) and subjects with alcoholic liver disease a mean ratio of 2.6 (range 1.1-11.2, median 2.0). The mean AST levels were 66 U/L and 152 U/L, and the mean ALT levels 91 U/L and 70 U/L, in the nonalcoholic steatohepatitis and alcoholic liver disease groups, respectively. Although the absolute aminotransferase levels were significantly different in the two groups (p < 0.05), the greatest difference was observed in the AST to ALT ratio (p < 0.000001). Subset analysis of patients with NASH revealed mean AST to ALT ratios of 0.7, 0.9, and 1.4 for subjects with no fibrosis, mild fibrosis, or cirrhosis, respectively. The differences among these ratios were statistically significant (p < 0.05). CONCLUSIONS: The AST to ALT ratio appears to be a useful index for distinguishing nonalcoholic steatohepatitis from alcoholic liver disease. Although values < 1 suggest NASH, a ratio of > or = 2 is strongly suggestive of alcoholic liver disease.

Alanine Transaminase↗

PubMed1981

Evaluation of the IFCC-recommended procedure for serum aspartate aminotransferase as modified for use with the centrifugal analyzer.

The IFCC-recommended procedure for aspartate aminotransferase (EC 2.6.1.1) was adapted to the centrifugal analyzer and evaluated during five years. The main hindrance to widespread use of the recommended method is the need for pre-incubation with pyridoxal phosphate. The present method includes a 10-min pre-incubation with pyridoxal phosphate. Extensive evaluation of the method with and without this pre-incubation confirms earlier reports that it eliminates some significant errors, especially for samples from patients with cardiac disease. However, the pre-incubation can be briefer than the recommended 10 min and still provide acceptable results.

Aspartate Aminotransferases↗

PubMed1980

Comparative study of dynamic structure of pig and chicken aspartate aminotransferases by measuring the rotational correlation time.

The rotational correlation time of two homologous cytoplasmic aspartate aminotransferase molecules isolated from pig and chicken hearts was obtained by spin-labeling technique. The maleimide and iodoacetamide spin-labels modifying external SH-groups of a protein were used. In the interpretation of ESR spectra a rotational motion of nitroxide group relative to the protein molecule was taken into account. To determine the macromolecule rotational correlation time two methods of the immobilization of a protein molecule were used: 1) by means of increasing protein solution viscosity and 2) by fixation of the protein molecule on adsorbent. From comparison of experimental and theoretical values of rotational correlation time it was conclude that the both enzymes exhibits an intramolecular flexibility.

Animals↗

PubMed1995

L-aspartate aminotransferase and L-asparaginase in rat lymph node: a histoenzymological and immunohistochemical study.

L-asparaginase and L-aspartate aminotransferase are both involved in the synthesis of L-aspartic acid. It has been observed that L-asparaginase is involved in the immunosuppressor morphine-dependent syndrome in lymphoid cells whereas L-aspartic acid blocks the development of this syndrome. The aim of the present study was to clarify the localization of L-AATase activity and L-asparaginase in rat lymph nodes using histoenzymological and immunohistochemical methods, respectively. No positive reaction was demonstrated for L-AATase while L-asparaginase shown to be present in lymphocytes and lymphoblastic cells. These observations lead us to suggest that L-asparaginase is the enzyme mainly responsible for the synthesis of the L-aspartic acid necessary for satisfying the living requirements of lymphoid cells. Therapeutically administered L-asparaginase could exert its action intracellularly after crossing the cell membrane.

Animals↗

PubMedDate not supplied

[Structural basis for differences in substrate specificity of aspartate aminotransferase isoenzymes].

X-Ray structural data concerning the substrate binding site of cytosolic chicken aspartate aminotransferase (AspAT) are reported. The structure of the complex of AspAT with the substrate-like inhibitor maleate has been refined at 2.2 A resolution. The lengths of hydrogen bonds between a bound molecule of maleate and side chains of amino acid residues in the active site are presented as well as other interatomic distances in the substrate binding site. The data obtained for the cytosolic AspAT have been compared with those for the mitochondrial chicken AspAT. It has been inferred that differences in substrate specificity of the AspAT isoenzymes are determined by interactions involving amino acid residues which are situated in the immediate vicinity of the active site and influence ionization or orientation of functional groups interacting with substrate. An explanation is suggested for different rates of transamination of aromatic amino acids in the active sites of the cytosolic and mitochondrial isoenzymes.

Amino Acids↗

PubMed1995

Characterization of a soybean cDNA clone encoding the mitochondrial isozyme of aspartate aminotransferase, AAT4.

A soybean leaf cDNA clone, pSAT2, was isolated by hybridization to a carrot aspartate aminotransferase (EC 2.6.1.1.; AAT) cDNA clone at low stringency. pSAT2 contained an open reading frame encoding a 47640 Da protein. The protein encoded by pSAT2 showed significant sequence similarity to AAT proteins from both plants and animals. It was most similar to two Panicum mitochondrial AATs, 81.5% and 82.0% identity. Alignment of the pSAT2-encoded protein with other mature AAT enzymes revealed a 25 amino acid N-terminal extension with characteristics of a mitochondrial transit peptide. A plasmid, pEXAT2, was constructed to encode the mature pSAT2 protein lacking the putative mitochondrial transit peptide. Escherichia coli containing the plasmid expressed a functional AAT isozyme which comigrated with the soybean AAT4 isozyme during agarose gel electrophoresis. Equilibrium sucrose gradient sedimentation of soybean extracts demonstrated that AAT4 specifically cofractionated with mitochondria. Antibodies raised against the pEXAT2-encoded AAT protein reacted with AAT4 of soybean and not with other AAT isozymes detected in soybean tissues, providing further evidence that clone pSAT2 encodes the soybean mitochondrial isozyme AAT4.

Amino Acid Sequence↗

PubMed1991

Autonomous folding and coenzyme binding of the excised pyridoxal 5'-phosphate binding domain of aspartate aminotransferase from Escherichia coli.

The coenzyme (PLP) binding domain (residues 47-329) of the dimeric aspartate aminotransferase from Escherichia coli was produced separately by recombinant DNA methods. It folded autonomously both in vivo and in vitro, that is, independently of the native N- and C-terminal extensions that combine to form the small domain of eAAT. The PLP-domain had one binding site for PLP of relatively high affinity involving a covalent bond to the protein. It was monomeric, although the major subunit-subunit interface at the 2-fold symmetry axis remained unchanged. This effect appears to be due mainly to the absence of the N-terminal extension that contains hydrophobic residues, which interact with the PLP-domain of the second subunit in the wild-type dimer. Judged by circular dichroism, fluorescence, and HPLC gel filtration at increasing concentrations of guanidinium chloride, the PLP-domain underwent a three-state unfolding transition (M' in equilibrium M'* in equilibrium U') involving a compact intermediate M'*. This behavior parallels the unfolding of the dissociated native monomer of cAAT.

Apoenzymes↗

PubMed1985

Effect of oral contraceptive use on the erythrocytic glutathione reductase and aspartate aminotransferase activities in women with or without clinical signs of vitamin deficiency.

The effect of the chronic use of combined oral contraceptives (OCs) on the "activity coefficients" (alpha = coenzyme-stimulated activity/basal activity) of erythrocytic glutathione reductase and aspartate aminotransferase was studied in 2 groups of 90 female volunteers each; 1 of the groups, from the state of Yucatan in southeast Mexico, presented clinical lesions of vitamin deficiency, while the other group, from Mexico City, did not have any clinical evidence of vitamin deficiency. One half of the women (45) in each group were chronic OC users and the other half were not. The results were analyzed comparing OC users with non-users in each location. For both glutathione reductase and aspartate aminotransferase, the Mexico City OC users had significantly higher (p 0.001) alpha values than nonusers, while in the Yucatan women, the alpha values were similarly high independent of OC use.

Americas↗

PubMed1979

Relative stabilities of purified human mitochondrial and cytoplasmic isoenzymes of aspartate aminotransferase in lyophilized materials.

Eight different pools of purified human mitochondrial and cytoplasmic isoenzymes of aspartate aminotransferase were prepared, to examine the effects of the following matrix variables: the matrix support material (bovine serum albumin and polyvinylpyrrolidone), endogenous pyridoxal concentration, and azide as an antimicrobial preservation. Storage temperatures of 25 and 37 degrees C were used as a rapid and convenient means of accelerating the degradation process. Activity of the enzyme was measured with and without pyridoxal in the reaction solution. We found that the mitochondrial isoenzyme was consistently more labile than the cytoplasmic isoenzyme under identical storage conditions. Both isoenzymes were more stable in matrixes containing bovine serum albumin than in those containing polyvinylpyrrolidone. No apparent difference in the stability of either isoenzyme was observed at matrix pyridoxal concentrations of 15 micromol/L and 150 micromol/L. Only the mitochondrial isoenzyme in matrixes containing bovine serum albumin and 15 micromol of pyridoxal per liter had increased activity (about 9%) when pyridoxal was added to the enzymatic reagent. The amount of activity in reconstituted specimens did not apparently change after 72 h at 4 degrees C.

Aspartate Aminotransferases↗

PubMed1992

Cloning and sequence analysis of cDNA encoding aspartate aminotransferase isozymes from Panicum miliaceum L., a C4 plant.

The cytosolic and mitochondrial isozymes of aspartate aminotransferase (AspAT) function in the C4 dicarboxylate cycle of photosynthesis. We constructed a cDNA library from leaf tissues of Panicum miliaceum, an NAD-malic-enzyme-type C4 plant and screened the library for AspAT isozymes. A full-length cDNA clone for cytosolic AspAT was isolated. This clone contains an open reading frame that encodes 409 amino acids. We also isolated two cDNA clones for different precursors of mitochondrial AspAT. Comparing these two sequences in the coding regions, we found 12 amino acid substitutions out of 28 base substitutions. The encoded amino acid sequences predict that mitochondrial AspAT are synthesized as precursor proteins of 428 amino acid residues, which each consist of a mature enzyme of 400 amino acid residues and a 28-amino-acid presequence. This prediction coincides with the observation that the in vitro translation product of the mRNA for mitochondrial AspAT was substantially larger than the mature form. A comparison of the amino acid sequences of the AspAT isozymes from P. miliaceum with the published sequences for the enzymes from various animals and microorganisms reveals that functionally and/or structurally important residues are almost entirely conserved in all AspAT species.

Amino Acid Sequence↗

PubMedDate not supplied

Longitudinal evaluation of aspartate aminotransferase in the crevicular fluid of implants with bone loss and signs of progressive disease.

Aspartate aminotransferase (AST) has been shown to be a promising host marker for periodontal disease progression. The aim of the present study was to analyze AST in the crevicular fluid (CF) of implants exhibiting peri-implantitis and to evaluate the association between AST levels and progressive attachment loss. Twenty patients who had received a total of 42 endosseous cylindric titanium implants were examined. Radiographic assessment of preexisting bone loss and clinical measurements, including electronic attachment of probing, presence or absence of plaque, bleeding on probing, and AST analysis in CF, were performed on 2 occasions 6 months apart. During this study period 13 of 168 sites in 7 patients experienced further loss of attachment greater than or equal to 1.0 mm (median 1.7 mm; interquartile range 0.4 mm). Evaluation of a positive AST test (> or = 300 microIU) in site-specific diagnosis revealed low positive (8%) and high negative predictive values (92%), with a sensitivity of 15% and a specificity of 83%. These results indicate that, in contrast to periodontal disease, the assessment of AST in peri-implant crevicular fluid may be of limited value as a diagnostic and prognostic marker for peri-implant disease.

Alveolar Bone Loss↗

PubMed1993

Cell-specific regulation of cytosolic aspartate aminotransferase by glucocorticoids in the rat kidney.

The basal expression and hormonal regulation of cytosolic aspartate aminotransferase (cAspAT) were investigated in the rat kidney. In adrenalectomized animals, the basal activity was highest in the renal cortex and in the inner stripe of the outer medulla (0.1-0.15 U/mg protein). The glucocorticoid analogue dexamethasone increased cAspAT activity about twofold in the cortex and in the inner stripe of the outer medulla but not in the papilla. A half-maximal increase in the activity was achieved at doses of approximately 5 micrograms/100 g body wt. The mineralocorticoid aldosterone did not modify the cAspAT activity. The cell specificity of the hormonal regulation was analyzed by in situ hybridization. In untreated adrenalectomized rats, a cAspAT cRNA probe labeled mainly the inner stripe of the outer medulla. After dexamethasone or hydrocortisone treatment, labeling was uniformly increased in this part of the medulla and was heterogeneously increased in the renal cortex. The specific increase in labeling within the cortex was shown to be confined to the distal convoluted tubule and the thick ascending limb. We conclude that, in addition to widespread basal expression, cAspAT is regulated by glucocorticoids in a highly cell-specific manner in the renal cortex. The enzyme may thus participate in the increased energy metabolism elicited by these hormones in these cells.

Adrenalectomy↗

PubMed1983

A comparative study of polyclonal and monoclonal antibodies for immunocytochemical localization of cytosolic aspartate aminotransferase in rat liver.

The rabbit antiserum and mouse monoclonal hybridoma antibody against porcine cytosolic aspartate aminotransferase (c-AAT) (or cytosolic glutamic oxaloacetic transaminase (c-GOT)) were produced and compared for the localization of c-AAT in rat liver. An indirect immunocytochemical technique was performed using peroxidase-conjugated goat immunoglobulin (Ig) G anti-rabbit IgG and peroxidase-conjugated rabbit IgG anti-mouse IgG as the second antibody. Rats were perfused with paraformaldehyde-lysine-periodate fixative and the liver fragments were immersed in 4% paraformaldehyde and transferred to 10% dimethyl sulfoxide overnight and subjected to cryostat sectioning. The rabbit IgG antibody, 3 individual monoclonal antibodies, and a mixture of these 3 monoclonal antibodies were applied to the tissue sections, respectively, using the same concentration. Under the same experimental conditions, the c-AAT was localized in each individual hepatocyte by both monoclonal and polyclonal antibodies. However, a mixture of three monoclonal antibodies gave stronger staining than a single monoclonal antibody; although two antibodies yield more intense staining than just one, it was still less intense than for three. The conventional rabbit polyclonal antibody against c-AAT produced more reaction product than the combined three monoclonal antibodies. It is concluded that for immunocytochemical study, the use of a single monoclonal antibody is sensitive enough to localize its tissue antigen under the present experimental condition. To obtain a stronger reaction product, a combination of several monoclonal antibodies, at least three or more, may give better staining.

Animals↗

PubMed1973

Purification and some properties of cytoplasmic aspartate aminotransferase from sheep liver.

1. A procedure for the purification of the cytoplasmic isoenzyme of aspartate aminotransferase from sheep liver is described. 2. The purified isoenzyme shows a single component in the ultracentrifuge at pH7.6 and forms a single protein band on agar-gel electrophoresis at pH6.3 or 8.6, as well as when stained for protein or activity after polyacrylamide-gel or cellulose acetate electrophoresis at pH8.8. 3. Immunoelectrophoresis on agar gel yields only one precipitin arc associated with the protein band, with rabbit antiserum to the purified isoenzyme. By immunodiffusion, cross-reaction was detected between the cytoplasmic isoenzymes from sheep liver and pig heart, but not between the cytoplasmic and mitochondrial sheep liver isoenzymes. 4. The s(20,w) of the enzyme is 5.69S and the molecular weight determined by sedimentation equilibrium is 88900; 19313 molecules of oxaloacetate were formed/min per molecule of enzyme at pH7.4 and 25 degrees C. 5. The amino acid composition of the isoenzyme is presented. It has about 790 residues per molecule. 6. The holoenzyme has a maximum of absorption at 362nm at pH7.6 and 25 degrees C. 7. A value of 2.1 was found for the coenzyme/enzyme molar ratio. 8. The purified enzyme revealed two bands of activity on polyacrylamide-gel electrophoresis at pH7.4 and an extra, faster, band in some circumstances. These bands occurred even when dithiothreitol was present throughout the isolation procedure. 9. Three main bands were obtained by electrofocusing on polyacrylamide plates with pI values 5.75, 5.56 and 5.35. 10. Structural similarities with cytoplasmic isoenzymes from other organs are discussed.

Amino Acid Sequence↗

PubMed1998

Characterization of a single soybean cDNA encoding cytosolic and glyoxysomal isozymes of aspartate aminotransferase.

A soybean cDNA clone, pSAT1, which encodes both the cytosolic and glyoxysomal isozymes of aspartate aminotransferase (AAT; EC 2.6.1.1) was isolated. Genomic Southern blots and analysis of genomic clones indicated pSAT1 was encoded by a single copy gene. pSAT1 contained an open reading frame with ca. 90% amino acid identity to alfalfa and lupin cytosolic AAT and two in-frame start codons, designated ATG1 and ATG2. Alignment of this protein with other plant cytosolic AAT isozymes revealed a 37 amino acid N-terminal extension with characteristics of a peroxisomal targeting signal, designated PTS2, including the modified consensus sequence RL-X5-HF. The second start codon ATG2 aligned with previously reported start codons for plant cytosolic AAT cDNAs. Plasmids constructed to express the open reading frame initiated by each of the putative start codons produced proteins with AAT activity in Escherichia coli. Immune serum raised against the pSAT1-encoded protein reacted with three soybean AAT isozymes, AAT1 (glyoxysomal), AAT2 (cytosolic), and AAT3 (subcellular location unknown). We propose the glyoxysomal isozyme AAT1 is produced by translational initiation from ATG1 and the cytosolic isozyme AAT2 is produced by translational initiation from ATG2. N-terminal sequencing of purified AAT1 revealed complete identity with the pSAT1-encoded protein and was consistent with the processing of the PTS2. Analysis of cytosolic AAT genomic sequences from several other plant species revealed conservation of the two in-frame start codons and the PTS2 sequence, suggesting that these other species may utilize a single gene to generate both cytosolic and glyoxysomal or peroxisomal forms of AAT.

Amino Acid Sequence↗

PubMed1982

Chemistry of the inactivation of cytosolic aspartate aminotransferase by serine O-sulfate.

The reaction of serine O-sulfate with cytosolic aspartate aminotransferase [John, R.A., & Fasella, P. (1969) Biochemistry 8, 4477] has been reinvestigated. As in the corresponding reaction with beta-chloroalanine [Morino, Y., Osman, A.M., & Okamoto, M. (1974) J. Biol. Chem. 249, 6684], the enzyme is inactivated over a 10-min period, and the absorption maximum at pH 5.4 shifts from 430 to 336 nm. Upon prolonged standing the peak shifts again over a period of 20 h to 455 nm, a behavior entirely similar to that reported by Morino et al. for beta-chloroalanine in the presence of 3 M formate. When the pH of either the 10-min product (1a) or the 20-h product (1b) is raised to 11 or above, a yellow, diffusible compound (2) is released from the protein. This compound as well as its dephosphorylation and reduction products has been isolated and studied by NMR spectroscopy. Compound 2 is identical with a compound formed from serine sulfate and glutamate decarboxylase by a similar reaction sequence [Likos, J.J., Ueno, H., Feldhaus, R.W., & Metzler, D.E. (1982) Biochemistry (preceding paper in this issue)] and is the product of an aldol condensation of pyruvate with pyridoxal phosphate. When the 20-h product 1b is reduced with sodium borohydride and then heated in a boiling water bath, a material identical with the reduction product of 2 is released. We propose that the 20-h product 1b consists of 2 bound to the enzyme. Pathways for the formation of the various compounds are proposed. These findings require a reevaluation of the mechanisms of action of many enzyme-activated inhibitors of pyridoxal phosphate dependent enzymes.

Aspartate Aminotransferases↗