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PubMed1987

Cytochemical demonstration of aspartate aminotransferase in the mossy-fibre system of the rat hippocampus.

A lead-salt procedure was used for the cytochemical demonstration of aspartate aminotransferase (AT) in the CA3 of the rat hippocampus. Cytoplasmic- and mitochondrial-AT isoenzymes were demonstrated in different neuronal structures, but not in astrocytes. Of special interest was the localization of cytoplasmic AT in most mossy-fibre boutons. This might indicate that cytoplasmic AT is responsible for the production of releasable glutamate in the glutamatergic/aspartatergic mossy fibre system.

Animals↗
PubMed1977

Suitability of commercial enzyme control sera for the quality control of activity determinations of L-aspartate aminotransferase and L-alanine aminotransferase in human serum.

Details of a systematic approach to suitability testing of commercial control sera are given for substrate optimized L-aspartate aminotransferase and L-alanine aminotransferase methods at 37 degrees C. Their acceptability for control purposes of standardized methods depends on: (1) the range of control values in relation to borderline values, (2) stability, (3) aspect, clarity, (4) NADH consumption in preincubation time, (5) blank activities, (6) kinetic data as half saturation constants and saturation curves, (7) influence of effectors, (8) isoenzyme pattern. These evaluation criteria are proposed for suitability testing. The term "representativeness" should be introduced as a special criterion for main characteristics of control materials. The authors want to point out the close connection with standardization of methods.

Absorption↗
PubMed1989

Concentration of creatine kinase and aspartate aminotransferase in the blood of wild mallards following capture by three methods for banding.

The concentration of the enzymes creatine kinase (CK) and aspartate aminotransferase (AST), that are released from damaged muscle, was measured in the blood of wild adult male mallards (Anas platyrhynchos) captured for banding in decoy and bait traps and by rocket net. The concentration of CK and to a lesser extent AST was elevated markedly in ducks captured by all methods, indicating muscle injury. The level of CK was significantly greater in ducks captured in decoy traps and rocket net than in those captured in bait traps. This elevation appeared to be related to the length of time the birds were restrained and to the method of restraint.

Animals↗
PubMedDate not supplied

[Activity of alanine- and aspartate-aminotransferases in organs of albino rats subjected to whole body gamma-irradiation and physical exercise].

The investigations of enzyme activity such as aspartate aminotransferase (AST, KE 2.6.1.1.) and alanine aminotransferase (ALT, KE 2.6.1.2) playing an important role in proteins metabolism were carried out in cell fraction of rat liver, myocardial and skeleton muscle after the influence of ionizing radiation (6 Gy) and the maximum physical loading. It was shown that physical loading furthered the increase of ALT-activity in all cell fractions except liver cytosol. And it was noted a strongly pronounced tendency of AST-activity to lowering, except muscle cell fractions. ALT-activity level in irradiated animals showed phase changes dependent on the term of observation and the kind of investigated tissues. The primary lowering of AST-activity in cell fractions of the investigated tissues is a conformity to natural laws of the gamma-irradiation influence on AST in most cases. It was shown that the physical tiredness made worse penetrated radiation action on the investigated enzymes.

Alanine Transaminase↗
PubMed1984

Phosphorus-31 nuclear magnetic resonance study on cytoplasmic aspartate aminotransferase from pig heart. A reinvestigation.

Striking differences of the environment of the phosphate group of pyridoxal-P in cytoplasmic and mitochondrial aspartate aminotransferase have been reported. Since most details of the three-dimensional structure of the active sites of these isozymes are identical, it seemed difficult to rationalize the reported differences. Therefore, the cytoplasmic isozyme was reinvestigated using 31P-NMR at 72.86 MHz. The 31P chemical shift of the cofactor of this isozyme was found to be pH-dependent with a pKa of 6.2. In the presence of 100 mM succinate or 100 mM glutarate, the 31P chemical shift of bound pyridoxal-P remains at 4.71 or 4.79 ppm, respectively, in the pH range from 5.0 to 8.0, indicating that the phosphate group of the cofactor appears to be in its dianionic form. Reduction of the internal pyridoxal-P Schiff's base dramatically increases the pKa of the phosphate group of the phosphopyridoxyl moiety of the protein to 8.3. Hence, our results on the cytoplasmic isozyme are similar to those reported for the mitochondrial isozyme.

Animals↗
PubMed2004

Effect of low-zinc status and essential fatty acids deficiency on the activities of aspartate aminotransferase and alanine aminotransferase in liver and serum of albino rats.

The effects of dietary deficiencies of zinc and essential fatty acids (EFAs) or both on aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were investigated in young growing rats. Four groups of albino rats were fed diets deficient in either EFA (4% hydrogenated coconut oil) or zinc (6 ppm) or both. The control diet was adequate in EFA (4% soybean oil) and zinc (100 ppm). The feeding trial lasted eight weeks and the activities of AST and ALT were determined in the liver and serum. EFA deficiency had no significant (p > 0.05) effect on liver AST. However, zinc and the double deficiencies depressed AST activity in the organ. Deficiencies of EFA, zinc and their combination depressed ALT activity in the liver significantly (p < 0.05) with a concomitant increase recorded in the serum. The data suggested alteration in endothelial permeability of the plasma membrane and thus leakage of membrane constituents in the tissue studied. It is therefore considered that these deficient diets may affect liver tissue negatively in view of the role of these enzymes in amino acid metabolism.

Alanine Transaminase↗
PubMed1978

The apoenzyme of aspartate aminotransferase and alanine aminotransferase in the serum of healthy persons and patients suffering from liver diseases.

In activity determination with addition of pyridoxal 5'-phosphate (P-5-P), aspartate aminotransferase (AST) activity increases by 6.5 U/l and that of alanine aminotransferase (ALT) by 2.5 U/l in the serum of healthy persons. This corresponds to a relative stimulation of initial activity by 37% and 15.2%, respectively. ApoAST activity in patients with chronic liver diseases is not changed as compared with that of healthy persons, the relative stimulation rate, however, is significantly smaller. ApoALT activity and corresponding relative stimulation is significantly greater as compared with healthy persons. In the case of acute viral hepatitis, a decrease of AST and ALT activity is followed by a decrease of apoenzyme activity in the course of disease. Diagnostic evidence of determinations of aminotransferase activities could not be improved by addition of P-5-P.

Alanine Transaminase↗
PubMed1989

Reactions of phosphonate analogs of pyridoxal phosphate with apo-aspartate aminotransferase.

We have investigated reactions of the 5-phosphonoethyl and 5-phosphonoethenyl analogs of pyridoxal 5'-phosphate in the coenzyme site of cytosolic aspartate aminotransferase. Acid dissociation constants and equilibrium constants for hydration and for tautomerization have been evaluated for these compounds. In confirmation of previous results, both compounds are partially active. They bind to apoenzyme well and undergo conversion in the presence of glutamate to amine forms which show induced circular dichroism comparable to that of native enzyme. A normal "external" Schiff base is evidently formed with 2-methylaspartate, but the amounts of quinonoid intermediate formed with erythro-3-hydroxyaspartate are less than those formed with pyridoxal phosphate. The pKa of the imine group of the enzyme reconstituted with the phosphonoethyl analog is more than two units lower than that in the native enzyme. Binding of the dicarboxylates glutarate, 2-oxoglutarate, and succinate shifts the pKa upward. The absorption spectra of the resulting complexes indicate the existence of at least three low pH species. A shift of 2.3 to 2.9 ppm to a lower frequency was observed for the 31P NMR signal upon binding of these dicarboxylates or of 2-methylaspartate. Enzyme containing the analogs crystallizes. Polarized absorption spectra suggest that the coenzyme has an orientation similar to that of pyridoxal phosphate in the native enzyme.

Amines↗
PubMed2000

The folding of nascent mitochondrial aspartate aminotransferase synthesized in a cell-free extract can be assisted by GroEL and GroES.

At 30 degrees C, the precursor to mitochondrial aspartate aminotransferase (pmAspAT) cannot fold after synthesis in rabbit reticulocyte lysate (RRL), a model for studying intracellular protein folding. However, it folds rapidly once imported into mitochondria. Guanidinium chloride denatured pmAspAT likewise cannot refold at 30 degrees C in a defined in vitro system. However, it refolds rapidly and in good yield in the presence of the intramitochondrial chaperone homologues GroEL and GroES. In this report, we demonstrate that GroEL and GroES can also facilitate the folding of nascent pmAspAT in reticulocyte lysate under conditions where it otherwise would not. When added alone, GroEL arrests the slow folding of nascent pmAspAT and inhibits import into mitochondria. These effects are significantly reversed by adding GroES. These observations suggest that added GroEL participates in an equilibrium with endogenous chaperones in the cytosol which inhibit folding and promote import competence. Native gel electrophoresis suggests that nascent pmAspAT exists in RRL as a heterogeneous population of partially folded species, some of which bind to added GroEL more readily than others. The GroEL-trapped species appear to be among the productive pmAspAT folding intermediates formed in RRL or they at least appear to equilibrate with these intermediates, since they become import competent after GroES-stimulated release from GroEL.

Animals↗
PubMed1992

Diagnostic characteristics of crevicular fluid aspartate aminotransferase (AST) levels associated with periodontal disease activity.

During a 2-year period pocket depth, probing attachment level, gingival index, and crevicular fluid aspartate aminotransferase (AST) levels were monitored in 25 previously treated periodontitis patients. Probing attachment level change was used retrospectively to identify sites where active periodontal destruction had occurred. The ability of crevicular fluid AST activities at 600, 800, 1000, and 1200 microIU levels to recognize active disease was investigated. Probing attachment level changes observed support the concept that the pattern of periodontal disease activity is episodic and infrequent. A loss of greater than or equal to 2 mm was found at 11% of all studied sites, whereas a gain of greater than or equal to 2 mm was noticed for 15% of sites. 2 subjects had 3 teeth that lost greater than or equal to 2 mm of attachment, whereas 15 subjects demonstrated no teeth with disease activity. The remaining 8 subjects had 1 or 2 sites that lost greater than or equal to 2 mm of attachment. Bayes's theorem and ROC curves were used to exemplify the sensitivity and the specificity of AST assessments. The AST 800 microIU demonstrated a sensitivity of 0.93 and specificity 0.68 and an odds ratio of 15.4 for attachment loss greater than or equal to 2 mm. Under the conditional probability of either 50%, 25% or 10% active disease prevalence, AST 800 microIU has a predictability of 73%, 50% and 24% respectively.

Aspartate Aminotransferases↗
PubMed2000

Aspartate aminotransferase: alanine aminotransferase ratio in chronic hepatitis C infection: is it a useful predictor of cirrhosis?

BACKGROUND: The clinical usefulness of the ratio of serum aspartate aminotransferase (AST) to alanine aminotransferase (ALT) has been explored in several liver disorders. It has been suggested that in patients with chronic hepatitis C virus (HCV) infection an AST:ALT > or = 1 has 100% specificity and positive predictive value in distinguishing cirrhotic from non-cirrhotic patients. Such statistical certainty attached to a simple biochemical test merits further evaluation. The present study, therefore, assessed the AST:ALT in patients with chronic HCV infection to determine the validity of the ratio in predicting cirrhosis and to correlate the ratio with the histological grade of necroinflammatory activity and fibrosis. METHODS: A retrospective analysis of 153 patients with chronic HCV infection was conducted. Serum biochemistry had been obtained within a mean of 4 weeks of liver biopsy. The histology was scored in terms of activity and fibrosis as described by Scheuer and correlated with AST:ALT. RESULTS: In 30 patients with cirrhosis, the mean AST:ALT (0.99 +/- 0.06) was higher than in 123 patients without cirrhosis (0.60 +/- 0.02; P < 0.001). A ratio > or = 1 had 95.9% specificity and 73.7% positive predictive value in distinguishing cirrhotic from non-cirrhotic patients, with a 46.7% sensitivity and 88.1% negative predictive value. The ratio also parallelled the Scheuer score with respect to fibrosis but not with respect to inflammation. CONCLUSION: Although relatively insensitive, an AST:ALT > or = 1 is highly specific but not diagnostic for the presence of cirrhosis in patients with chronic HCV infection. The ratio reflects the grade of fibrosis in these patients.

Adult↗
PubMed2001

Association of early onset periodontitis microbiota with aspartate aminotransferase activity in gingival crevicular fluid.

OBJECTIVES: The objective of this study was to determine the relationship between the activity of the enzyme aspartate aminotransferase (AST) in gingival crevicular fluid (GCF) using the colorimetric PerioGard (PTM) test and the subgingival microflora in early onset periodontitis lesions. MATERIAL AND METHODS: The study population consisted of 25 otherwise healthy individuals exhibiting early onset periodontitis (EOP). In each patient four experimental sites were identified comprising one deep periodontal pocket (PD >5 mm) randomly chosen in each quadrant. Bacterial samples were obtained from the experimental sites, consecutively cultured anaerobically and in 10% CO(2) using selective and nonselective media. Isolates were characterized to species level by conventional biochemical tests and various identification kits. Clinical measurements as well as AST activity, assessed either as positive or negative using the PTM, were recorded at the same sites. RESULTS: Sixty-two sites exhibited AST positive and 38 AST negative activity. Analysis of bacterial counts using the ANOVA (Mann Whitney U-test) showed that Streptococcus intermedius, Peptostreptococcus micros, Campylobacter concisus, Bacteroides forsythus, Camplobacter gracilis, Campylobacter rectus and Selenomonas sputigena were significantly higher in sites with AST-positive activity. The odds ratio of having high prevalence of S. intermedius, P. micros, C. concisus, B. forsythus, C. gracilis, C. rectus and S. sputigena in the presence of a positive AST site was very high (range: 3.5-17.0). Streptococcus sanguis, Actinomyces naeslundii, Gemella morbillorum, Capnocytophaga gingivalis, Veillonella parvula, Fusobacterium varium, Eubacterium lentum and Prevotella oralis were detected in significantly higher proportions in sites with AST negative activity and manifested a negative odds ratio in the presence of AST positive sites. The logistic regression analysis revealed that smoking and bleeding upon probing showed a significant association with AST activity, while plaque and suppuration were not found to be significant predictors of AST activity. The co-infection of Porphyromonas gingivalis, B. forsythus and P. micros, or P. gingivalis, B. forsythus and C. rectus were found to be significantly associated with the AST activity (p<0.001). AST positive sites revealed significantly higher occurrence of co-infections by P. gingivalis, B. forsythus, S. sputigena or by P. gingivalis, B. forsythus, S. intermedius than AST negative sites (p<0.001). P. gingivalis, B. forsythus, A. naeslundii co-infection was found significantly higher in the AST negative sites (p<0.001). CONCLUSIONS: The present study found a high level of agreement between the presence of putative periodontal pathogens and positive AST scores at periodontal sites that clinically were considered to be potentially disease active. Prospective studies should be performed to confirm the findings.

Adult↗
PubMed1984

Interactions between carbamyl phosphate synthase-I-mitochondrial aspartate aminotransferase and palmitoyl-CoA.

Carbamyl phosphate synthase-I and glutamate dehydrogenase both form a complex with mitochondrial aspartate aminotransferase. Instead of these two enzymes competing for the aminotransferase, carbamyl phosphate synthase-I enhances glutamate dehydrogenase-aminotransferase interaction. This suggests that a complex can be formed between all three enzymes. Since this complex is stable in the presence of substrates and modifiers of the three enzymes, it could conceivably convert NH+4 produced from aspartate into carbamyl phosphate. Furthermore, since carbamyl phosphate synthase-I is the predominant protein in liver mitochondria, it could play a major role in placing the aminotransferase and glutamate dehydrogenase in close proximity. Malate removes glutamate dehydrogenase from the tri-enzyme complex and thus could play a role in determining whether glutamate dehydrogenase interacts with carbamyl phosphate synthase-I or is available to participate in reactions with the Krebs cycle. Palmitoyl-CoA has a high affinity for both carbamyl phosphate synthase-I and glutamate dehydrogenase. ATP and malate which, respectively, decrease and enhance binding of palmitoyl-CoA to glutamate dehydrogenase, respectively decrease and enhance the ability of this enzyme to compete with carbamyl phosphate synthase-I for palmitoyl-CoA. Since carbamyl phosphate synthase-I is present in high levels in liver mitochondria and has a high affinity for palmitoyl-CoA, it could play a major role as a reservoir for palmitoyl-CoA.

Acyl Coenzyme A↗
PubMedDate not supplied

The primary structure of mitochondrial aspartate aminotransferase from pig heart: peptides obtained by cleavage with thermolysin and chymotrypsin.

The production, purification and analysis of peptide derived by digestion of mitochondrial aspartate aminotransferase with thermolysin and chymotrypsin are described. Despite the complexity of the peptide mixture obtained and the relative shortness of the fragments produced, these digests proved to be very useful for the completion of the primary structure determination of the enzyme. In fact, information for 87% of the total structure was contributed by thermolytic peptides, and for 89% by the chymotryptic ones. Moreover some of these peptides were essential for elucidating controversial points of the sequence.

Amino Acid Sequence↗
PubMed1995

Effects of aminoguanidine and pyridoxal phosphate on glycation reaction of aspartate aminotransferase and serum albumin.

Effects of aminoguanidine (AG) on binding of glucose and pyridoxal phosphate (PLP) to albumin, and on glycation reaction of cytosolic aspartate aminotransferase (cAST) were examined in an in vitro system. AG was found to inhibit not only glycation of albumin but binding of PLP to albumin, indicating that distribution of PLP into tissues is inhibited by AG. AG bound to PLP directly to produce a new compound, and in this manner AG inhibited cAST activity. AG could also inhibit glycation of cAST and the extent of inhibition was varied with sugars used. It appears that, although AG is a useful inhibitor of glycation proteins, it may be toxic from the viewpoints of vitamin B6 as an essential nutrient and also PLP-dependent enzymes.

Animals↗
PubMed1991

Cytochemical demonstration of aspartate aminotransferase activity in the rat retina.

The mitochondrial (m-AAT) and the cytoplasmic (c-AAT) isoenzyme activities of the glutamate synthesizing enzyme aspartate aminotransferase have been localized in the rat retina on the ultrastructural level using enzyme histochemistry. Reaction product of c-AAT was found selectively in cone pedicles, in presynaptic terminals of a subpopulation of amacrine cells and of horizontal cell processes, which are connected to rods. Rod spherules, terminals of cone-related horizontal cells and of bipolar cells reacted negatively, as well as ganglion cells, nerve fibre layer and optic nerve, m-AAT reaction product was found in all neuronal structures, most densely in the photoreceptor inner segments. The localization of c-AAT activity is in accordance with its presumed meaning in the production of releasable glutamate.

Animals↗
PubMed2000

Non-enzymatic glycosylation (or glycation) and inhibition of the pig heart cytosolic aspartate aminotransferase by glyceraldehyde 3-phosphate.

Glyceraldehyde 3-phosphate (Glyc3P), a glycolytic intermediate, non-enzymatically glycosylated (or glycated) and inhibited the pig heart cytoplasmic aspartate aminotransferase (cAAT). Glyc3P (5.0 mM) decreased cAAT activity by 47% after 1 min at 23 degrees C. cAAT activity remained unchanged after a 24h incubation with either glucose 6-phosphate (5.0 mM) or ribose 5-phosphate (5.0 mM). Increasing the incubation pH from 6.4 to 7.8 or the incubation temperature from 23 degrees C to 50 degrees C enhanced Glyc3P's inhibitory effect on cAAT activity. Glyc3P (250-500 microM) decreased the thermal stability of cAAT as evidenced by lowering the Tm or temperature that caused a 50% irreversible loss of cAAT activity (69 degrees C, control; 58.5 degrees C, 500 microM Glyc3P). Glyc3P decreased cAAT amino group content and increased glycation products, which were measured by adduct formation, fluorescence and protein crosslinking.

Animals↗