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At least 883 records · Page 49Linked to original sources
PubMed1987

[Distribution of alanine and aspartate aminotransferases, gamma-glutamyltransferase, lactate dehydrogenase, alkaline phosphatases and creatine kinase in the main organs of adult goats and kids].

In adult ewes, the distribution of enzymes in the liver, kidney, spleen, pancreas, muscle, lung and myocardium was very similar to that in cows or sheep: aspartate aminotransferase (ASAT), alanine aminotransferase (ALAT), lactate dehydrogenase (LDH) and creatine kinase (CK) were mainly in skeletal muscles and the myocardium, while gamma-glutamyl transferase (GGT) and alkaline phosphatases (PAL) predominated in the kidneys. Age-related changes of tissue enzyme patterns were dominated by a dramatic decrease of liver ALAT in adults whereas this enzyme was liver-specific in one month old animals; a decrease of muscle LDH and CK, and an increase of kidney GGT and ALP were also observed in adults.

Aging↗
PubMed1977

Glutamate dehydrogenase and aspartate aminotransferase in Trypanosoma cruzi.

1. The cultured, epimastigote-form of Trypanosoma cruzi contains NADP-linked glutamate dehydrogenase (EC 1.4.1.4), with a molecular weight of about 280,000, similar to the enzyme from Plasmodium chabaudi and different from the enzymes from higher animal sources. 2. T. cruzi also contains aspartate aminotransferase (EC 2.6.1.1), with properties similar to those of the enzyme from mammals. 3. The concerted action of the transaminase and glutamate dehydrogenase might be responsible for the production of NH3 which characterizes the protein catabolism in T. cruzi.

Animals↗
PubMed2003

Strain and catalysis in aspartate aminotransferase.

The notion of "ground-state destabilization" has been well documented in enzymology. It is the unfavourable interaction (strain) in the enzyme-substrate complex, and increases the k(cat) value without changing the k(cat)/K(m) value. During the course of the investigation on the reaction mechanism of aspartate aminotransferase (AAT), we found another type of strain that is crucial for catalysis: the strain of the distorted internal aldimine in the unliganded enzyme. This strain raises the energy level of the starting state (E+S), thereby reducing the energy gap between E+S and ES(++) and increasing the k(cat)/K(m) value. Further analysis on the reaction intermediates showed that the Michaelis complex of AAT with aspartate contains strain energy due to an unfavourable interaction between the main chain carbonyl oxygen and the Tyr225-aldimine hydrogen-bonding network. This belongs to the classical type of strain. In each case, the strain is reflected in the pK(a) value of the internal aldimine. In the historical explanation of the reaction mechanism of AAT, the shifts in the aldimine pK(a) have been considered to be the driving forces for the proton transfer during catalysis. However, the above findings indicate that the true driving forces are the strain energy inherent to the respective intermediates. We describe here how these strain energies are generated and are used for catalysis, and show that variations in the aldimine pK(a) during catalysis are no more than phenomenological results of adjusting the energy levels of the reaction intermediates for efficient catalysis.

Aspartate Aminotransferases↗
PubMed1992

[The mechanisms of the neutrophil suppression of creatine kinase and aspartate aminotransferase activities in rat skeletal muscles].

Abdominal neutrophils effect on rat skeletal muscle m. soleus was investigated in vitro. The incubation was carried out in Hanks balanced solution within 24 hrs. It was a release of proteins from m. soleus 1 hr later. Creatine kinase (CK) and aspartate aminotransferase (AAT) activities increase was detected in incubation medium. The neutrophils released their proteins quicker than muscles. A dramatic inhibition of CK and AAT activities took place during coincubation of m. soleus and neutrophils. Zymosan-activated cells had a higher inhibition potency in comparison to nonactivated neutrophils. Analysis of proteinase and myeloperoxidase activities in incubation medium has given evidence that CK and AAT inhibition by non-activated neutrophils mainly depends on cell-secreted proteinases. Zymosan-activated neutrophil inhibition of CK and AAT consists of proteinases and myeloperoxidase effects. AAT appeared to be more resistant than CK to the damage by neutrophils. The used approach failed to demonstrate the direct damage effect of neutrophils on m. soleus, but the described enzyme inhibition mechanism can take place in vivo during leukocyte infiltration of skeletal muscles after intensive muscular activity.

Animals↗
PubMed1985

Determination of serum aspartate aminotransferase with pyridoxal 5'-phosphate in the Technicon SMAC and Du Pont aca compared and correlated with the IFCC recommended method.

Inexpensive improvements in continuous-flow analytical apparatus can eliminate some perplexing inconsistencies and limitations in the use of the Technicon SMAC instrument for measuring the activity in serum of aspartate aminotransferase (EC 2.6.1.1) in the presence of pyridoxal 5'-phosphate. In addition, a calibration procedure based on values for this enzyme obtained by a modified IFCC method can be used to calibrate both the Technicon SMAC and the Du Pont aca instruments to produce excellent correlation between the two.

Aspartate Aminotransferases↗
PubMed1985

Evaluation of the erythrocyte aspartate aminotransferase activity coefficient as an indicator of the vitamin B-6 status of postpubertal gilts.

In two experiments, postpubertal gilts, individually housed in gestation stalls, were fed daily 1.9 kg of a purified diet providing 0.45, 1.5, 2.1 or 83 mg of vitamin B-6/d. The erythrocyte aspartate aminotransferase (more commonly known as glutamic-oxaloacetic transaminase) activity coefficient (EGOT-Ac) of gilts fed the low vitamin B-6 diet (0.45 mg vitamin B-6/d) for 121 d increased 200%, while the EGOT-Ac of gilts fed the high vitamin B-6 diet (83 mg vitamin B-6/d) remained unchanged. Two gilts were fed the low vitamin B-6 diet for 241 d at which time hair loss was observed. Muscle glutamic-oxaloacetic transaminase activity was reduced 75% in vitamin B-6-deficient gilts. The EGOT-Ac of gilts consuming 2.1 mg vitamin B-6/d was 100% greater than that of control animals (83 mg vitamin B-6/d). These findings indicate that the current NRC estimated vitamin B-6 requirement for mature swine (1.8 mg vitamin B-6/d) is inadequate. Prior intake of excess vitamin B-6 did not prevent the subsequent development of a vitamin B-6 deficiency.

Animals↗
PubMed1988

Creatine kinase:aspartate aminotransferase activity ratio as an indicator of the source of an increased creatine kinase activity.

Although measurements of creatine kinase isoenzyme 2 (CK-MB) are often used to diagnose acute myocardial infarction, their sensitivity and specificity are less than 100%. Because skeletal muscle contains more CK and less aspartate aminotransferase (AST) than cardiac muscle, the CK/AST ratio might provide a useful adjunct in evaluating the source of a supranormal value for CK. I established the following decision levels in a retrospective study of 342 patients: ratios less than 14 (if total CK was 300-1200 U/L), less than 20 (CK 1201-2000 U/L), or less than 25 (CK greater than 2000 U/L) suggested myocardial infarction, with a sensitivity of 95% and a specificity of 65%. In a validation study with 277 additional patients, liver disease and alcohol abuse caused erroneous results, leading to exclusion of 22% of these patients. In the remaining cases, sensitivity was 94%, specificity 90%. The CK/AST ratios changed little with time, suggesting that a single value would be adequate for evaluating patients with increased CK.

Aspartate Aminotransferases↗
PubMed1983

[Development of aspartate aminotransferase, alanine and gamma-glutamyltransferase in the blood serum of dairy cows during the last month of pregnancy and the puerperium in relation to liver function].

Over the period of two years, the blood serum of dairy cows from three localities was examined repeatedly for the activities of aspartate aminotransferase (EC 2.6.1.1) (AST), alanine aminotransferase (EC 2.6.1.2) (ALT) and gammaglutamyltransferase (EC 2.3.2.1) (GMT). First examinations were performed two to four weeks before the expected term of delivery, the repeated examinations between the sixth and eighth week after delivery. The results obtained were used to calculate AST/ALT and GMT/ALT indexes in the studied group of animals (n = 12). As found out, the decrease in these indexes or the equality of values from the sixth to the eighth week after delivery, as compared with the period of two to four weeks prior to delivery, were connected with the clinically detectable disturbances of puerperium, i. e. inflammable discharge from the reproductive organs of dairy cows; this was observed even in the cases when the enzymatic activity was within the references standards.

Alanine Transaminase↗
PubMed1975

Population differences of aspartate aminotransferase and peptidase in the bay mussel Mytilus edulis.

This investigation has demonstrated considerable heterogeneity among populations and some heterogeneity within populations in the distribution of alleles at two variant loci of Mytilus edulis. Although the causes of this variation remain obscure, some speculations have been made on the basis of available data. A cline for aspartate aminotransferase (AAT) alleles has been observed on the Pacific Coast. An immigration model has been proposed to explain the atypical ecological and genetic characteristics of large mussels found on Amchitka Island, Alaska. Marked differences were found in the distribution of peptidase alleles among collections from Southern California, the North Pacific Ocean, and New Jersey. Deviations from random distribution of phenotypes observed in comparisons made between large and small mussels from the New Jersey collection may reflect selection operating on these loci in this population.

Alleles↗
PubMed1988

Pentylenetetrazole inhibits glutamate dehydrogenase and aspartate aminotransferase, and stimulates GABA aminotransferase in homogenates from rat cerebral cortex.

The mechanism by which pentylenetetrazole provokes convulsions in animals has been investigated by measuring its influence in vitro on the activities of several enzymes of glutamate metabolism in rat brain homogenates. Pentylenetetrazole does not affect the specific activities of glutamine synthetase, glutaminase, or glutamate decarboxylase; it inhibits those of glutamate dehydrogenase and aspartate aminotransferase, and stimulates that of gamma-aminobutyric acid (GABA) aminotransferase. The overall consequence of the action of pentylenetetrazole on the activities of these enzymes should be an increase in the concentration of glutamate and a decrease in that of GABA. This modulation of glutamate and GABA metabolism by pentylenetetrazole could contribute to the triggering of convulsions.

4-Aminobutyrate Transaminase↗
PubMed1999

Carnosine prevents glyceraldehyde 3-phosphate-mediated inhibition of aspartate aminotransferase.

Post-mitotic tissues, such as the heart, exhibit high concentrations (20 mM) of carnosine (beta-alanyl-l-histidine). Carnosine may have aldehyde scavenging properties. We tested this hypothesis by examining its protective effects against inhibition of enzyme activity by glyceraldehyde 3-phosphate (Glyc3P). Glyc3P is a potentially toxic triose; Glyc3P inhibits the cardiac aspartate aminotransferase (cAAT) by non-enzymatic glycosylation (or glycation) of the protein. cAAT requires pyridoxal 5-phosphate (PyP) for catalysis. We observed that carnosine (20 mM) completely prevents the inhibition of cAAT activity by Glyc3P (5 mM) after brief incubation (30 min at 37 degrees C). After a prolonged incubation (3.25 h) of cAAT with Glyc3P (0.5 mM) at 37 degrees C, the protection by carnosine (20 mM) persisted but PyP availability was affected. In the absence of PyP from the assay medium, cAAT activities (plus Glyc3P) were 95 +/- 18.2 micromol/min per mg protein (mean +/- SD), minus carnosine and 100 +/- 2.4, plus carnosine; control activity was 172 +/- 3.9. When PyP (1.0 microM) was included in the assay medium, cAAT activities (plus Glyc3P) were 93 +/- 14.8, minus carnosine and 151 +/- 16.8, plus carnosine, P < 0. 001; control activity was 180 +/- 17.7. These data, which showed carnosine moderating the effects of both Glyc3P and PyP, suggest that carnosine may be an endogenous aldehyde scavenger.

Aspartate Aminotransferases↗
PubMed1990

Isoenzyme profiles of creatine kinase, lactate dehydrogenase, and aspartate aminotransferase in the diabetic heart: comparison with hereditary and catecholamine cardiomyopathies.

STUDY OBJECTIVE: The aim was to investigate the redistribution of isoenzymes, clinically important markers of myocardial necrosis, in the diabetic heart and compare it with that investigated in other types of cardiomyopathies. DESIGN: Myocardial isoenzyme activity of creatine kinase (CK), lactate dehydrogenase (LD) and aspartate aminotransferase (AST) was measured in animals with diabetic, hereditary, and catecholamine cardiomyopathies. SUBJECTS: Diabetic rats (4 and 8 weeks after intravenous streptozotocin, n = 21), Bio 14.6 hamsters (30, 90, 160 and 240 days old, n = 29), and rats injected with isoprenaline (0.25, 0.5 and 1.0 mg.kg-1.d-1 for 3 weeks, n = 20) were used. Controls were age matched intact animals (n = 8-11). MEASUREMENTS AND MAIN RESULTS: Total CK and CK MM activity decreased in all groups. CK MB and BB decreased by 62 and 52% in diabetic rats, but increased by 40 and 33% in Bio hamsters and by 9 and 96% in isoprenaline treated rats. Thus the CK-B subunit decreased by 61% in diabetics and increased by 33 and 38% in Bio and isoprenaline groups, while the CK-M subunit decreased in all groups. Mitochondrial CK decreased in diabetic and isoprenaline groups. Total LD activity increased in diabetics and decreased in Bio. LD-H subunit increased by 21% in diabetics and decreased by 19 and 18% in Bio and isoprenaline groups. Accordingly the proportion of LD-M subunit, an index of anaerobic metabolism, decreased in diabetics and increased in Bio and isoprenaline groups. Changes in CK-M and CK-B subunits and the LD-M proportion in diabetic heart were normalised by insulin. Total AST activity decreased in diabetics because of the reduction in mitochondrial AST. CONCLUSIONS: Increased LD-M proportion and CK-B observed in Bio and isoprenaline groups may be a metabolic "compensation" to decreased myocardial perfusion and substrate. Decreased LD-M proportion and CK-B in the diabetic heart was insulin dependent and may indicate either lack of "compensation" to myocardial ischaemia or absence of ischaemia per se. Decreased myocardial CK and CK MB activity possibly causes underestimation of enzymatically assessed infarct size in the diabetic heart.

Animals↗
PubMed1998

Cytosolic aspartate aminotransferase gene is a member of the glucose-regulated protein gene family in adipocytes.

Stress controls the expression of a cohort of genes. Among these, the glucose-regulated protein (GRP) genes are specifically activated by glucose deprivation, reducing agents, glycosylation block, intracellular calcium or ex vivo incubations of tissues or cells. We demonstrate that these stimuli induce the expression of the cytosolic aspartate aminotransferase gene in adipocytes by a process involving the region of the promoter between -2405 and -26 bp. Therefore this transaminase is a new member of the GRP family.

3T3 Cells↗
PubMed1989

A computer program to determine diagnostic decision thresholds and likelihood ratios illustrated with aspartate aminotransferase activities after a myocardial infarction.

We describe an enhancement of our earlier computer program which allows calculation of decision thresholds, sensitivity and specificity, and likelihood ratios of negative and positive test results for any chosen value of sensitivity or specificity. The program will also plot continuous receiver operating characteristic and decision level curves which permit examination of the contours created by using all the available data. We illustrate the value of these routines by showing that the sensitivity and specificity of serum aspartate aminotransferase changes during the course of a myocardial infarction.

Aspartate Aminotransferases↗