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PubMed1977

Mapping of the aspartate and aromatic amino acid aminotransferase genes tyrB and aspC.

Co-transduction experiments using P1-mediated reciprocal and three-factor crosses have been used to map two mutations affecting the aspartate and aromatic amino acid aminotransferases of Escherichia coli. tyrB-, which inactivates the tyrosine-repressible component of these activities is co-transducible with metA and malB; the gene order is metA-malB-tyrB. aspC-, which inactivates the nonrepressible aminotransferase with high activity for aspartate, maps between and is co-transducible with serC and pyrD.

Aspartate Aminotransferases↗

PubMed1987

Purification and properties of the cytosolic and mitochondrial forms of aspartate aminotransferase and malate dehydrogenase from rat heart.

The present work describes the purification from rat heart of the mitochondrial and cytosolic forms of the enzymes of the malate--aspartate shuttle, aspartate aminotransferase (EC 2.6.1.1) and malate dehydrogenase (EC 1.1.1.37), by a single procedure after the preparation of the original crude extract. In 10 purification steps, the four enzymes were obtained electrophoretically pure in yields ranging from 6 to 54% of their respective isoenzyme levels in the crude extract. Apoenzymes were formed from the aminotransferases by reacting them with cysteine sulfinate and dialyzing. Complete reconstitution was obtained after a brief incubation with pyridoxal phosphate. All four enzymes are dimers. The mitochondrial isoenzymes are of slightly lower molecular weight than their respective cytosolic forms. Michaelis constants and maximal velocities were derived by the use of primary and secondary plots. In general, the properties of the enzymes from rat heart are similar to the properties of the enzymes from other animal sources.

Animals↗

PubMed1986

Mitochondrial and cytoplasmic aspartate aminotransferase enzyme release in the calcium paradox.

The release of mitochondrial and cytoplasmic aspartate aminotransferase (AST) enzymes from the myocardium was studied in the isolated rabbit heart under conditions of the calcium paradox. Four different periods of calcium-free perfusion for 10, 15, 20, and 25 min were selected to produce different degrees of the calcium paradox and the associated myocardial damage which was indicated by impairment in the left ventricular contractile function. Calcium-free perfusion periods of less than 20 min were associated with partial recovery of ventricular function, while periods of 20 min or greater were associated with little or no recovery of contraction after reperfusion with calcium. Mitochondrial (ASTm) and cytoplasmic (ASTc) aspartate aminotransferase were released from the heart beginning within 1 min of reintroduction of Ca2+. The cumulative amount of ASTm release was about one-tenth the amount of ASTc release. The cumulative amount of ASTm and ASTc released were significantly (p less than 0.05) related to the duration of calcium-free perfusion. The time to 90% of maximum AST release was slightly longer for ASTm compared with ASTc (6.8 +/- 0.6 vs. 5.7 +/- 0.5 min, 0.10 greater than p greater than 0.05). ASTc but not ASTm correlated significantly (p less than 0.05) with total protein release from the myocardium, while ASTm was not as consistently related to protein loss. The cumulative amount of ASTm and ASTc were inversely related to the extent of recovery of left ventricular contractile function. Disparities did occur as the longest duration of the calcium-free period, which did not produce any further damage to left ventricular function, was nonetheless associated with more enzyme release from the myocardium.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1986

Correlation between pyridoxal-5'-phosphate levels and the percentage activation of aspartate aminotransferase enzyme in haemolysate and plasma during in vitro incubation studies with different B6 vitamers.

Conflicting results using erythrocyte aminotransferase (eAST) stimulation to assess vitamin B6 nutritional status in patients with less severe B6 deficiencies are common. It has been claimed that the presence of different B6 vitamers may modify the activation of eAST by pyridoxal-5'-phosphate (PLP) leading to stimulatory or even inhibitory effects. To investigate the possible role of this phenomenon in producing inconsistent AST stimulations, aliquots of whole blood were incubated with equivalent amounts of different B6 vitamers, and the AST stimulation was correlated with the concentrations of PLP, measured by high-performance liquid chromatography. At the end of the incubation period the erythrocytes and plasma were separately analyzed. The conversion of non-PLP B6 vitamers to PLP, by the erythrocytes, was similar (approximately 70%) for all B6 vitamers used in the incubation experiments. The newly formed PLP accumulated in the erythrocytes, but the percentage activation of AST did not change significantly from the basal levels, in spite of the presence of increased levels of PLP and other B6 vitamers used for incubation. When PLP was used in the incubation studies, all of it was retained by the plasma and was associated with a marked suppression of plasma AST stimulation. To determine the degree to which plasma and erythrocyte AST was dose-dependent, plasma and haemolysates were incubated with increasing concentrations of PLP. A very significant inverse relationship was obtained in plasma between AST stimulation and PLP even at modest PLP levels, while haemolysates required incubation with much higher PLP concentrations to demonstrate the same effect. Since plasma PLP is considered to be the most reliable indicator of B6 nutritional status in man, our findings suggest that plasma percentage AST stimulation more closely reflects the B6 nutritional status than erythrocyte AST stimulation test which may reflect B6 status only in severe, longstanding B6 deficiencies. Conflicting results using erythrocyte AST stimulations may be attributed to the insensitivity of red cell AST to changes in PLP content. It is unlikely that the presence of non-PLP B6 vitamers in haemolysate may affect the percentage stimulation of aminotransferase enzymes by PLP.

Aspartate Aminotransferases↗

PubMed1990

Quantitative distributions of aspartate aminotransferase and glutaminase activities in the guinea pig cochlea.

Distributions of aspartate aminotransferase and glutaminase activities in the guinea pig cochlea have been examined with use of quantitative microchemical techniques to evaluate their roles in cochlear energy metabolism and neurotransmission. Other enzyme activities analyzed were those of choline acetyltransferase and malate dehydrogenase. It is concluded that aspartate aminotransferase activity appears to be especially concerned with cochlear energy metabolism, while glutaminase activity may function in transmitter metabolism in the guinea pig cochlea. Neither enzyme shows a clear association with the olivocochlear bundle.

Animals↗

PubMed1995

The C-S lysis of L-cysteine conjugates by aspartate and alanine aminotransferase enzymes.

One biotransformation pathway which is responsible for the generation of mutagenic and cytotoxic metabolites is that of the C-S lysis (CSL) of L-cysteine conjugates. Thirteen cysteine S-conjugates, synthesised in our laboratories, were incubated with porcine heart aspartate aminotransferase (ASAT) and alanine aminotransferase (ALAT), and the C-S lyase activity for each enzyme-substrate combination was determined. ASAT and ALAT were shown to exhibit CSL activity. It was also demonstrated that this activity was inhibited in the presence of the pyridoxal phosphate (PLP)-dependent enzyme inhibitor amino(oxyacetic acid) (AOAA) confirming the pyridoxal phosphate dependent mechanism by which C-S lysis is known to take place. Since the activities of these enzymes are used as biomarkers for the assessment of organ damage, the potential interaction of L-cysteine conjugates with them may suppress their activity through direct inhibition.

Alanine Transaminase↗

PubMed1991

Population distribution profiles of the activities of blood alanine and aspartate aminotransferase in the normal F344 inbred rat by age and sex.

Data on the blood enzyme activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were collected from control male and female F344 rats participating in toxicity studies at 17, 30, 56, 80 and 106 weeks of age. The data were skewed to the right with significant deviation from normality. Applying the Box-Cox transformation, it was concluded that approximately normal distributions could be obtained by using the reciprocal transformation. In general, the males showed a greater degree of heterogeneity for both enzymes. Enzyme activities at 17 weeks were lowest for both ALT and AST. There was a high correlation between the activities of blood ALT and AST, with some animals showing dramatic transient increases. Significant differences among studies with respect to the enzyme activities in rats of the same age were demonstrated.

Aging↗

PubMed2002

IFCC primary reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 degrees C. International Federation of Clinical Chemistry and Laboratory Medicine. Part 5. Reference procedure for the measurement of catalytic concentration of aspartate aminotransferase.

This paper is the fifth in a series dealing with reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 degrees C and the certification of reference preparations. Other parts deal with: Part 1. The Concept of Reference Procedures for the Measurement of Catalytic Activity Concentrations of Enzymes; Part 2. Reference Procedure for the Measurement of Catalytic Concentration of Creatine Kinase; Part 3. Reference Procedure for the Measurement of Catalytic Concentration of Lactate Dehydrogenase; Part 4. Reference Procedure for the Measurement of Catalytic Concentration of Alanine Aminotransferase; Part 6. Reference Procedure for the Measurement of Catalytic Concentration of Gamma-Glutamyltransferase; Part 7. Certification of Four Reference Materials for the Determination of Enzymatic Activity of Gamma-Glutamyltransferase, Lactate Dehydrogenase, Alanine Aminotransferase and Creatine Kinase at 37 degrees C. A document describing the determination of preliminary upper reference limits is also in preparation. The procedure described here is deduced from the previously described 30 degrees C IFCC reference method. Differences are tabulated and commented on in Appendix 3.

Aspartate Aminotransferases↗

PubMed1991

Influence of 5-[2-(N,N-dimethylamino)ethoxy]-7-oxo-7H-benzo(C)fluorene hydrochloride (benflurone) on the activity of rat liver aspartate and alanine aminotransferases.

The influence of repeated s.c. administration of the cytostatic 5-[2-(N,N-dimethylamino)ethoxy]-7-oxo-7H-benzo(c)fluorene hydrochloride (benflurone, 25 mg/kg body weight daily) on the activities of aspartate and alanine aminotransferases (AST, ALT) per g of tissue, and protein concentration in the liver of adult male rats was studied. During the first week of benflurone administration, the activities of ALT and AST decreased by 2/3 and 1/3, respectively, in comparison with controls while the protein concentration did not show any substantial change. No in vitro influence of benflurone on AST and ALT was found even at the highest concentration tested (10(-4) M). The significance of the aminotransferase decrease after treatment with benflurone and possible participation of these changes in the side- or cytostatic effects of the compound are considered.

Alanine Transaminase↗

PubMedDate not supplied

Effect of cortisone on aspartate and alanine aminotransferases in a desert lizard.

1. Liver and serum aspartate aminotransferase (GOT) and alanine aminotransferase (GPT) activities were measured in a hibernating desert lizard, Uromastix hardwickii. The levels of both enzymes were found to be lower in hibernation than during the active period, particularly in the liver. 2. After intramuscular injection of 2 mg of cortisone acetate there was a rapid rise in the levels of these enzymes with a peak of 18 hours (GOT) and 12 hours (GPT). 3. The response of both enzymes to cortisone was much greater during the active period than during hibernation. 4. GOT showed a much more rapid and greater response to cortisone than GPT. This is in contrast to the response of rat liver where GPT is more responsive to this hormone. 5. These studies indicate that the transferase enzymes of this lizard differ from those of the rat in their sensitivity and time of response to cortisone.

Alanine Transaminase↗

PubMed1993

Immunoglobulin-complexed aspartate aminotransferase.

We report a case of increased aspartate aminotransferase (AST, EC 2.6.1.1; GOT) in a 17-year-old girl which persisted for 3 years. The patient was healthy, but a high level of serum AST was detected during a school health check. Further examination revealed that AST was increased to as high as 259 IU/l while alanine aminotransferase (ALT) was normal. Immunoelectrosyneresis and immunoprecipitation methods revealed that this atypical AST combined with IgG--kappa, lambda globulin and formed macromolecular complexes. Including the present case, 26 cases of IgG-complexed AST have been reported. It is important to be aware of this syndrome, and thereby avoid unnecessary examinations and therapies.

Adolescent↗

PubMedDate not supplied

[The importance of aminotransferases and platelets count in non-invasive evaluation stages of chronic hepatitis C].

143 patients with chronic hepatitis C were investigated. The following two parameters were determined: the asparate to alanine aminotransferase ratio and the asparate aminotransferase to platelets count index. A liver biopsy was performed for every patient and stages of liver fibrosis were evaluated. Both parameters confirmed a positive correlation with liver fibrosis, which can be useful in predicting the progression of chronic hepatitis C.

Adult↗

PubMed2002

High alanine aminotransferase is associated with decreased hepatic insulin sensitivity and predicts the development of type 2 diabetes.

It has been proposed that liver dysfunction may contribute to the development of type 2 diabetes. The aim of the present study was to examine whether elevated hepatic enzymes (alanine aminotransferase [ALT], aspartate aminotransferase [AST], or gamma -glutamyltranspeptidase [GGT]) are associated with prospective changes in liver or whole-body insulin sensitivity and/or insulin secretion and whether these elevated enzymes predict the development of type 2 diabetes in Pima Indians. We measured ALT, AST, and GGT in 451 nondiabetic (75-g oral glucose tolerance test) Pima Indians (aged 30 +/- 6 years, body fat 33 +/- 8%, ALT 45 +/- 29 units/l, AST 34 +/- 18 units/l, and GGT 56 +/- 40 units/l [mean +/- SD]) who were characterized for body composition (hydrodensitometry or dual-energy X-ray absorptiometry), whole-body insulin sensitivity (M), and hepatic insulin sensitivity (hepatic glucose output [HGO] during the low-dose insulin infusion of a hyperinsulinemic clamp) and acute insulin response (AIR) (25-g intravenous glucose challenge). Sixty-three subjects developed diabetes over an average follow-up of 6.9 +/- 4.9 years. In 224 subjects, who remained nondiabetic, follow-up measurements of M and AIR were available. At baseline, ALT, AST, and GGT were related to percent body fat (r = 0.16, 0.17, and 0.11, respectively), M (r = -0.32, - 0.28, and -0.24), and HGO (r = 0.27, 0.12, and 0.14; all P < 0.01). In a proportional hazard analysis with adjustment for age, sex, body fat, M, and AIR, higher ALT [relative hazard 90th vs. 10th centiles (95% CI): 1.9 (1.1-3.3), P = 0.02], but not AST or GGT, predicted diabetes. Elevated ALT at baseline was associated prospectively with an increase in HGO (r = 0.21, P = 0.001) but not with changes in M or AIR (both P = 0.1). Higher ALT concentrations were cross-sectionally associated with obesity and whole-body and hepatic insulin resistance and prospectively associated with a decline in hepatic insulin sensitivity and the development of type 2 diabetes. Our findings indicate that high ALT is a marker of risk for type 2 diabetes and suggest a potential role of the liver in the pathogenesis of type 2 diabetes.

Adipose Tissue↗

PubMed1986

Liver investigation in 149 asymptomatic patients with moderately elevated activities of serum aminotransferases.

The accidental finding of raised levels of serum aminotransferase levels may lead to extensive investigations of the liver in apparently healthy people. To identify diagnostic groups and their need for investigations, we have evaluated the results of all investigative procedures carried out in 149 asymptomatic patients with persistently raised serum levels of aminotransferases. Fatty liver was found in 64%. These patients often had a high body weight. A high alcohol intake and diabetes mellitus were also noted. Chronic active or persistent hepatitis was found in 20% of the patients. Six per cent had cirrhosis, 4% had alpha 1-antitrypsin deficiency, and 3.5% had hemochromatosis. Apart from ferritin, alpha 1-antitrypsin, and markers for hepatitis B, blood tests were of little value for distinguishing among different diagnostic groups. This was the case also for the imaging procedures, and neither liver scintigraphy nor ultrasonography was a reliable source of diagnostic information. The results of our study indicate that diagnosis in this group of patients cannot be made without liver biopsy.

Alanine Transaminase↗

PubMed1997

Vitamin E improves the aminotransferase status of patients suffering from viral hepatitis C: a randomized, double-blind, placebo-controlled study.

UNLABELLED: Vitamin E has been shown to protect against liver damage induced by oxidative stress in animal experiments. Based on our previous findings of diminished vitamin E levels in patients suffering from viral hepatitis, we treated 23 hepatitis C patients refractory to alpha-interferon therapy with high doses of vitamin E (2 x 400 IU RRR-alpha-tocopherol/day) for 12 weeks. STUDY DESIGN: pro-spective randomized double-blind crossover design. Clinical parameters including alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were determined for monitoring the disease state, in parallel vitamin E plasma levels and plasma lipids were determined. The plasma levels of the alpha-tocopherol were increased about 2-fold in all 23 patients. In 11 of 23 patients the clinical parameters indicative of liver damage were improved during the phase of vitamin E treatment (48% responders). ALT levels in responders were lowered by 46% and AST levels were lowered by 35% after 12 weeks of vitamin E treatment. Cessation of vitamin E treatment was followed by a rapid relapse of ALT and AST elevation, whereas retreatment led to a reproducible ALT decrease by 45% and AST decrease of 37% after a 6 months followup. Since vitamin E is non-toxic even at elevated doses ingested over extended periods, we suggest the treatment of patients refractory to alpha-interferon therapy suffering from hepatitis C with vitamin E as a supportive therapy.

Alanine Transaminase↗

PubMed1982

Effect of treatment with pyridoxine on aspartate aminotransferase activities in pyridoxine-deficient rat tissues.

In rat liver, 90% of the aspartate aminotransferase is present as the holoenzyme. In pyridoxine deficiency, the ratio of holoenzyme activity to total activity is markedly reduced, but after pyridoxine injection it was found to rapidly increase, although the total enzyme activity remained low for a few days. The activities of aspartate aminotransferase isozymes in pyridoxine-deficient rat tissues and the effect of pyridoxine treatment on their activities were examined. The intestinal enzyme activities of pyridoxine-deficient rats were readily reconstituted in the presence of pyridoxal phosphate in vitro, but the enzyme activities in liver and muscle in the deficient rats required several days for complete recovery, suggesting that active enzyme was synthesized de novo in these tissues.

Animals↗

PubMed1984

Effect of administration of triiodothyronine on aspartate aminotransferase in pyridoxine-deficient rats.

The state of thyroid function and the effect of triiodothyronine (T3) administration on aspartate aminotransferase isozymes in the livers of rats fed on a diet with or without pyridoxine were examined. Decreased thyroid function in pyridoxine-deficient rats was demonstrated using malic enzyme as a marker of thyroid function in the liver. Administration of T3 increased cytosolic aspartate aminotransferase in the liver of pyridoxine-deficient rats, but not of control rats.

Animals↗

PubMed1985

Effect of pyridoxine administration on the induction of cytosolic aspartate aminotransferase in the liver of rats treated with hydrocortisone.

The effects of pyridoxine and hydrocortisone administrations on the rate of synthesis of cytosolic aspartate aminotransferase in adrenalectomized pyridoxine-deficient rat livers were examined. Induction of cytosolic aspartate aminotransferase by hydrocortisone was observed 6 to 10 h after the injection. Treatment with pyridoxine daily for 6 days but not for the 2 days, resulted in suppression of the enzyme synthesis. Similar suppression of enzyme synthesis was observed in rats without hydrocortisone treatment. The activity of tryptophan oxygenase, which is known to be induced by glucocorticoid and does not contain pyridoxal phosphates, was higher in the livers of pyridoxine-deficient rats than in that of controls. The possible effects of pyridoxal phosphate on the action of glucocorticoid are discussed based on the results.

Adrenalectomy↗