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At least 667 records · Page 37Linked to original sources
PubMed1993

Aspartate aminotransferase and tylosin biosynthesis in Streptomyces fradiae.

Aspartate aminotransferase as well as valine dehydrogenase and threonine dehydratase was required for the biosynthesis of tylosin in Streptomyces fradiae NRRL 2702. The biosynthesis of these enzymes and tylosin production were repressed by high concentrations of ammonium ions. The change in specific tylosin production rates in batch cultures with different initial concentrations of ammonium ions showed patterns similar to those of the specific production rates of aspartate aminotransferase, valine dehydrogenase, and threonine dehydratase. Aspartate aminotransferase has been purified by acetone precipitation, DEAE-cellulose, hydroxyapatite, and preparative electrophoresis chromatographies. The purified enzyme (120 kDa) consisted of two subunits identical in molecular mass (54 kDa) and showed homogeneity, giving one band with a pI of 4.2 upon preparative isoelectric focusing. The enzyme was specific for L-aspartate in the forward reaction; the Km values were determined to be 2.7 mM for L-aspartate, 0.7 mM for 2-oxyglutarate, 12.8 mM for L-glutamate, and 0.15 mM for oxaloacetate. The enzyme was somewhat thermostable, having a maximum activity at 55 degrees C, and had a broad pH optimum that ranged from 5.5 to 8.0. The mode of action was a ping-pong-bi-bi mechanism.

Amino Acid Oxidoreductases↗
PubMed1996

Inactivation of brain and kidney aspartate aminotransferases by S-(1,2,-dichlorovinyl)-L-cysteine and by S-(1,1,2,2,-tetrafluoroethyl)-L-cysteine.

Long-term exposure to trichloroethylene can cause kidney cancer in experimental animals and humans. In addition, dichloroacetylene (a breakdown product of trichloroethylene) is nephrotoxic and neurotoxic. Both trichloroethylene and dichloroacetylene are metabolized in part to the corresponding cysteine S-conjugate (i.e. S-(1,2-dichlorovinyl)-L-cysteine) which is toxic. Cysteine S-conjugate beta-lyases convert S-(1,2,dichlorovinyl)-L-cysteine to pyruvate, ammonia and a reactive fragment that adds to macromolecules, depletes cellular thiols and causes lipid peroxidation. We now show that S-(1,2-dichlorovinyl)-L-cysteine and another nephrotoxic cysteine S-conjugate, S-(1,1,2,2-tetrafluoroethyl)-L-cysteine, inactive purified cytosolic aspartate aminotransferase and purified alanine aminotransferase. These cysteine S-conjugates also inactive aspartate aminotransferase in cytosolic and mitochondrial fractions of rat brain and kidney. The present results suggest that some halogenated xenobiotics may be toxic in part through their conversion to the corresponding cysteine S-conjugate which inactivates key pyridoxal 5'-phosphate-containing enzyme.

Alanine Transaminase↗
PubMedDate not supplied

Seroprevalence of hepatitis C virus infection and evaluation of serum aminotransferase levels among haemodialysis patients in Izmir, Turkey.

The seroprevalence of hepatitis C virus (HCV) infection was investigated among haemodialysis (HD) patients. Mean serum aminotransferase levels were also compared over 3 months in HCV-seropositive patients with and without viraemia, as well as in HCV-seronegative HD patients and HCV-seropositive, non-uraemic, viraemic patients. Seroprevalence of HCV infection was 19% among the 437 HD patients tested. Of the 61 HD HCV-seropositive, hepatotoxic medication- and alcohol-free patients, 38 (62%) were found to be viraemic, using quantitative HCV-RNA, on at least one occasion. Mean serum aminotransferase levels were significantly higher in viraemic HD patients (compared with non-viraemic patients), suggesting that HCV-RNA positivity is an important predictor of increased enzyme activity in these patients. As expected, aminotransferase levels in HCV-seropositive HD patients tended to be lower than levels in HCV-seropositive non-uraemic patients.

Adult↗
PubMed1990

Hepatocellular integrity in swine after prolonged desflurane (I-653) and isoflurane anesthesia: evaluation of plasma alanine aminotransferase activity.

Desflurane, formerly known as I-653 (CF2H-O-CFH-CF3), is a new inhalation anesthetic derived by fluorine substitution for the alpha-ethyl chlorine of isoflurane (CF2H-O-CClH-CF3). The lower solubility and increased stability of desflurane provided by the C-F bond lessen biotransformation to potentially hepatotoxic metabolites. Repeated administration of desflurane to rats, with or without induced hepatic enzymes, does not result in evidence of hepatic injury. In the recent study we extended the tests for liver cell injury to another species, the pig. Our test included prolonged exposure to desflurane or isoflurane, both in the absence and presence of commonly used adjuvants. We measured plasma alanine aminotransferase activity in eight young female swine anesthetized in random order with desflurane (0.8-1.6 MAC) and isoflurane (0.7-1.4 MAC), for a total dose of about 5.5 MAC-hours of each anesthetic, 3-8 days apart. Plasma alanine aminotransferase activities remained in the normal range, and were not significantly greater over baseline values in samples drawn immediately after, 4 h after, or 3-8 days after (mean +/- SD, 6.1 +/- 2.1) the administration of either anesthetic was discontinued after the first study with either desflurane or isoflurane. Five additional pigs were given a mean total dose of 9.7 MAC-hours of desflurane or isoflurane in conjunction with succinylcholine, N2O, fentanyl, naloxone, atracurium, thiopental, edrophonium, and atropine. No changes in plasma alanine aminotransferase activity were detected in blood samples drawn at termination of the anesthesia, 24 h later, and 4-7 days later (mean +/- SD, 5.8 +/- 1.3).(ABSTRACT TRUNCATED AT 250 WORDS)

Alanine Transaminase↗
PubMed1977

Determination of the activity of aminotransferases: comparison of two buffer systems with and without supplementary pyridoxal-5'-phosphate.

A comparison was made between the aminotransferase activities of a number of plasma or serum samples in 4 reaction media: phosphate buffer, phosphate buffer + pyridoxal-5'-phosphate, tris buffer and tris buffer + pyridoxal-5'-phosphate. The reactions were carried out in the various buffer systems on the same day at 35 degrees C on an automatic kinetic enzyme system (AKES, Vitatron, Dieren, the Netherlands). The highest enzymic activity of both aminotransferases is observed in tris buffer + pyridoxal-5'-phosphate. The activity is about 10--15% higher than in phosphate buffer + pyridoxal-5'-phosphate. Without supplementary pyridoxal-5'-phosphate the differences between both buffer systems are lower or absent. It appears necessary, therefore, to determine the activity of both aminotransferases in a buffer system with tris and to add pyridoxal-5'-phosphate, since assays should be carried out in the presence of optimal concentrations of any of the necessary factors.

Alanine Transaminase↗
PubMed1984

Clinical and diagnostic significance of aspartate aminotransferase isoenzymes in sera of patients with liver diseases.

Serum aspartate aminotransferase isoenzymes were measured in 123 hospital patients with various liver diseases, using a new and simple immunochemical method. Our findings show the usefulness of this determination in estimating the severity of hepatic damage, especially if accompanied by the measurement of other mitochondrial enzymes. During hepatic damage, the cytoplasmic isoenzyme is found in greater quantities than the mitochondrial isoenzyme, but the level of the latter increases to a greater extent in acute liver diseases. Moreover, the values of mitochondrial aspartate aminotransferase activity and the ratio of mitochondrial to total aspartate aminotransferase in alcoholic hepatitis are higher than expected if so-called hepatic enzymes commonly measured in serum are considered. These results indicate that there is significant mitochondrial damage in alcoholic hepatitis.

Adult↗
PubMed1984

Aspartate aminotransferase increases in crevicular fluid during experimental periodontitis in beagle dogs.

A ligature-induced periodontitis model employing the beagle dog was used to study the levels of aspartate aminotransferase (AST) in crevicular fluid before and after ligation. A significant increase in AST level occurred in crevicular fluid 2 weeks after ligation whereas no increase of enzyme was found in serum. Enzyme levels in crevicular fluid were 10- to 100-fold higher than in serum. Dental plaque did not appear to be the source of the enzyme. Since aspartate aminotransferase has been documented as a marker of cellular injury arising during heart disease and liver disease, this study suggests that aspartate aminotransferase, in like fashion, reflects cellular damage arising from active periodontal disease.

Animals↗
PubMed1997

Glycation and inactivation of aspartate aminotransferase in diabetic rat tissues.

Glycated cytosolic aspartate aminotransferase was detected in the liver and kidney of streptozotocin diabetic rats using a boronate affinity column for adjacent cis-hydroxyl groups and an immunoblotting technique. The enzymatic activity and amount of immunoreactive substance were determined in the liver, kidney, and erythrocytes of diabetic and control rats. The ratio of enzymatic activity to the amount of enzyme was lower in diabetic rat tissue than in that in the control rats. It has been suggested that there is an inactive aspartate aminotransferase molecule in the tissues of diabetic rats. We therefore suggest that the cytosolic aspartate aminotransferase was inactivated in the diabetic rat tissues by a glycation reaction, accompanied by an impairment in glucose utilization.

Alkaline Phosphatase↗
PubMed1975

Partial purification and characterization of aspartate aminotransferases from seedling oat leaves.

As relatively little information is available on the properties of aspartate aminotransferase from photosynthetic tissue, isolation and characterization of the two major electrophoretically distinct forms of this enzyme from seedling oat leaf homogenates were undertaken. These two forms are designated I for the more anionic form and II for the less anionic form. Form I, 80 to 90% of the total activity, has been purified to a specific activity of 120 mumol/min/mg of protein (1100-fold) and is estimated to be 90 to 95% homogeneous, as judged by analytical polyacrylamide gel electrophoresis. Form II, 10 to 20% of the total activity, has been purified to a specific activity of approximately 6 mumol/min/mg of protein (300-fold). Both forms exhibit optimal activity at pH 7.5. Michaelis constants do not differ greatly between forms I and II and are similar to those reported for the pig heart cytosolic enzyme as well as aspartate aminotransferase from other plant sources. A molecular weight of 130,000 for the purified aspartate aminotransferase I was estimated by sedimentation equilibrium centrifugation; molecular weights of the two forms are similar as estimated by sucrose density gradient centrifugation. No activation by pyridoxal phosphate has been observed during purification.

Aspartate Aminotransferases↗
PubMedDate not supplied

Aspartate aminotransferase from wheat germ: purification and kinetic properties.

A convenient method for the purification of aspartate aminotransferase [L-aspartate-2-oxoglutarate aminotransferase (EC 2.6.1.1)] from wheat germ is described. An overall purification of 150 fold was achieved. On polyacrylamide gel electrophoresis at pH 8.9 the purified enzyme revealed two protein bands both provided with enzymatic activity. The holoenzyme is readily resolved on conversion to the aminic form and gel-filtration. The apoenzyme is reactivated by pyridoxal-5-phosphate. Kinetic data indicate that a Ping-Pong mechanism is operative similar to that found for the tyrosine aminotransferase by Litwack and Cleland (1968). Phosphate ion behaves as a competitive inhibitor towards the coenzyme. The relatively low affinity between coenzyme and apoenzyme from wheat germ allowed the determination of the dissociation constants for coenzymes (pyridoxal-5'-phosphate and pyridoxamine-5'-phosphate) and of the inhibition constant for phosphate.

Aspartate Aminotransferases↗
PubMed1975

Effect of bicarbonate buffer on the activity of cytoplasmic and mitochondrial alanine aminotransferase.

1. Bicarbonate stimulates the activity of rat brain cytoplasmic and mitochondrial alanine aminotransferase (EC 2.6.1.2) probably due to the enhanced affinity for its substrates. 2. Under the same conditions, the activity of crystalline aspartate aminotransferase was inhibited. 3. The role of bicarbonate buffer in regulation of alanine aminotransferase activity and synthesis of alanine are discussed.

Alanine Transaminase↗
PubMed1975

A systematic approach to enzyme assay optimization illustrated by aminotransferase assays.

We have developed a systematic approach to optimization of reagent concentrations for assays of alanine aminotransferase and aspartate aminotransferase: (a) Michaelis constants describing the initial-velocity kinetics of the coupled enzyme reactions were evaluated by a nonlinear least-squares fit of the appropriate equation to measured enzyme activities. Activities of more than 50 normal and pathological sera were measured at 30 degrees C. (b) These kinetic equations are used to calculate the set of reagent amino- and keto-acid concentrations that all yield a selected fraction of the theoretical maximum enzyme velocity. An optimal pair is determined by defining an additional criterion, such as minimal reagent cost or minimal concentration to Km ratio. (c) The optimum amounts of reagent NADH and coupling enzyme, being a function of desired pre-incubation and measurement intervals, maximum aminotransferase activity to be measured, and endogenous keto-acid concentration, are determined by computer simulation. An approximate relationship and an exact method for computing assay lag time are presented, along with experimentally measured endogenous keto-acid concentrations in serum. All procedures may be applied to other enzyme assays if appropriately modified.

Alanine Transaminase↗
PubMedDate not supplied

The effect of a single intense effort on the activity of aminotransferases and concentration of free amino acids in the plasma of rats.

Untrained rats were subjected to a single intense physical effort. In the plasma the activity of alanine aminotransferase, aspartate aminotransferase, and the concentrations of amino acids: glycine, cystine, alanine and leucine with isoleucine were measured. The results were compared with the data obtained in a control group. Despite lack of statistically significant differences in the activity of aminotransferases and concentration of amino acids between these groups a correlation was found between the activity of AIAT and alanine concentration in the animals after exercise. The concentration of alpha-amino nitrogen was decreased statistically significantly in the group of animals subjected to intensive exercise.

Alanine↗
PubMed2002

In vitro glycation of aminotransferases: a process closely depending on the employed experimental conditions.

The aim of the present study is to investigate the influence of various experimental conditions, i.e., two different concentrations of D-fructose as a rapidly glycating substance and three incubation temperatures, on the glycation reaction of alanine aminotransferase (ALT, EC 2.6.1.2) and aspartate aminotransferase (AST, EC 2.6.1.1) expressed by decreasing catalytic activities of the enzymes during a 56 day in vitro incubation period. D-fructose in the concentration of 50 mmol/l did not inhibit the catalytic activity of either enzyme at 4 degrees C, partially inhibited AST activity in samples incubated at 25 degrees C (to 40% of the initial activity), and completely inhibited this enzyme at 37 degrees C at the end of the incubation period. In the presence of the same concentration of D-fructose, ALT showed no catalytic activity after 35 days at 25 degrees C or after 10 days at 37 degrees C. In 500 mmol/l D-fructose, complete AST inhibition was observed after 35 days (25 degrees C) or 20 days (37 degrees C), and no ALT activity was found on day 20 at either 25 degrees C or 37 degrees C. Taking into account the highest possible stability of enzymes, we suppose that a three-week observation of their residual catalytic activity in the presence of 50 mmol/l D-fructose at the temperature of 25 degrees C seems to be the most prospective experimental design for future glycation studies with aminotransferases under the influences of drugs.

Alanine Transaminase↗
PubMedDate not supplied

[Aspartate- and alanine-aminotransferase in early development of keta].

We studied the activities of the marker enzymes of physiological state and adaptive reactions, aspartate and alanine aminotransferases, in early development of the keta Oncorhynchus keta. Aspartate aminotransferase with pH optima 6.8, 7.0, 7.6, and 8.0 and alanine aminotransferase with pH optima 7.0, 7.4, 7.6, 7.8, 8.0, and 8.2 were found in the eggs, larvae, and fry. The succession of enzymes with different pH takes place during ontogenesis, as well as stage specific changes in their activity. The maximum enzymatic activity was recorded in the larvae during their rise for "afloat." A correlation was established between the dynamics of enzymatic activity and soluble nitrogen and amine nitrogen contents.

Alanine Transaminase↗
PubMed1975

[The activity of aminotransferases in serum and cerebrospinal fluid in neurological diseases (author's transl)].

The activities of the aminotransferases, GOT and GPT, were determined in the serum and cerebrospinal fluid of patients with Parkinson's disease, Huntington's chorea, Wilson's disease, amyotrophic lateral sclerosis (ALS), Friedreich's ataxia, phenylketonuria, and head injuries. 1. In patients with Huntington's chorea the activity of SGOT was lower than in controls (P = 0.02); in Friedreich's ataxia LGPT activity was decreased (P less than 0.001); in patients suffering from ALS SGOT (P = 0.005), SGPT (P less than 0.001) and LGOT (P less than 0.001) activities were increased. 2. Long-term treatment of Parkinson's disease and Wilson's disease with L-dopa resulted in an increase in SGOT, LGOT, and SGPT activity over approximately 2 months, with subsequent normalization of these enzyme activities in spite of continued therapy. Guanidine treatment led to an increase in aminotransferase activities in patients with ALS. Penicillamine caused a decrease in SGOT and SGPT activities in Wilson's disease. These results illustrate the necessity of taking therapeutic measures into account in the interpretation of data on aminotransferase activities.

Alanine Transaminase↗