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PubMed1986

Development of aminotransferase activities in the serum of young rats born to normal females and to females exposed to intermittent hypoxia during pregnancy.

In the rat, aspartate aminotransferase (GOT) and alanine aminotransferase (GPT) activity increase during early postnatal ontogenesis. The development of these enzyme activities also remains normal in young whose mothers were repeatedly exposed to altitude hypoxia at a simulated altitude of 5 000 m during the whole of pregnancy.

Alanine Transaminase↗

PubMed1987

The stereospecific labilization of the C-4' pro-S hydrogen of pyridoxamine 5'-phosphate is abolished in (Lys258----Ala) aspartate aminotransferase.

Reconstitution of wild-type apoaspartate aminotransferase from Escherichia coli with [4'-3H]pyridoxamine 5'-phosphate results in stereospecific release of the pro-S C-4' 3H to the solvent. The reaction follows first-order kinetics (t1/2 = 15 min at pH 7.5 and 25 degrees C), its rate constant being similar to that found previously with mitochondrial aspartate aminotransferase from chicken (Tobler, H.P., Christen, P., and Gehring, H. (1986) J. Biol. Chem. 261, 7105-7108). Substituting the active site residue Lys258 by alanine via site-directed mutagenesis yields a catalytically inactive enzyme (Malcolm, B. A., and Kirsch, J. F. (1985) Biochem. Biophys. Res. Commun. 132, 915-921). This mutant enzyme fails to release any measurable 3H from bound [4'-3H]pyridoxamine 5'-phosphate. The data are consistent with earlier proposals that Lys258 is indispensable for the ketimine/aldimine tautomerization, and corroborate the previous conclusion that 3H exchange from enzyme-bound pyridoxamine 5'-phosphate mechanistically corresponds to the deprotonation at C-4' of the ketimine intermediate during the transamination reaction.

Alanine↗

PubMed1988

Studies on some kinetic parameters of aminotransferases in tissues of the snail, Pila globosa (Swainson) during malathion intoxication.

The aspartate and alanine aminotransferases in the tissues of the snail, Pila globosa showed high catalytic potentials (low Km and high Vmax) during malathion exposure in vivo. In vitro addition of different concentrations of malathion did not influence aminotransferase activity. The results are discussed in relation to the regulative influence of the intracellular environment of the cell.

Alanine Transaminase↗

PubMed1988

[Effect of electromagnetic fields on the living body. II. Changes in alanine and aspartate aminotransferase activities in subcellular fractions of the liver of guinea pigs].

The 50 Hz frequency electric field was applied to guinea pigs at different times of the day. The electric field effects upon the alanine and asparagine aminotransferase in supernatant, mitochondrial and nuclear fractions of guinea pig liver were observed. The highest increase in alanine aminotransferase activity was observed in the mitochondrial fraction, whereas asparagine transferase exhibited the highest activity increase in the supernatant fraction. Those changes may be indicative of adverse effects of electric field upon the liver cell metabolism.

Alanine Transaminase↗

PubMed1987

Alteration in aminotransferase levels in rats after acute hepatic injury.

Measurement of serial aspartate aminotransferase (AST) and alanine aminotransferase (ALT)--formerly GOT and GPT--in both serum and urine, were carried out in rats with hepatocellular injury induced by ingestion of carbon tetrachloride. Contrary to the accepted clinical observations, the AST was initially higher than the serum ALT. Also, the clearance of AST from blood to urine was more rapid than that of ALT. This difference in enzyme excretion resulted in a more persistent elevation of ALT than of AST in the serum after hepatic injury. The persistent elevation of serum ALT correlates well with the timing of the clinical observation of higher ALT in patients with hepatitis.

Alanine Transaminase↗

PubMedDate not supplied

[Aspartate aminotransferase activity as dependent on the degree of serum dilution].

Dependence of the enzymatic reaction rate V. catalyzed by aspartate aminotransferase, on concentration of standard human blood serum Moni-trol I ("Dade", Switzerland) was studied. In the range of moderate dilutions, which did not exceed 1.3-times, the V value altered in accordance with the blood serum concentration C. Under conditions of extensive dilutions dependence of V on blood serum concentration became complicated. The non-linear type of V dependence on blood serum concentration appears to be due to deaggregation of the enzyme molecules with formation of more active fragments as a result of blood serum dilution. Two parameters should be used for characteristics of blood serum aspartate aminotransferase activity: the enzymatic activity of undiluted blood serum as well as the ratio between specific activities of the enzyme in an associated from and the products of its dissociation, i.e. when C-1 and C-0, respectively.

Aspartate Aminotransferases↗

PubMed1979

[Kinetics of the aspartate-aminotransferase reaction catalyzed by free and immobilized cells of E. coli].

The kinetics of the aspartate-aminotransferase reaction were studied, using free and immobilized cells of E. coli, strain 85 as an enzyme source. It was shown that the reaction is limited by mass transport of the reagents through the bacterial cell membrane even at high concentrations of the substrates in the surrounding solution. The polyacrylamide gel-incorporated cells of E. coli, strain 85 catalyze the aspartate-aminotransferase reaction more effectively as compared to free or destroyed cells. In the latter case the reaction is characterized by the following kinetic parameters: the effective values of the stationary rate of the product accumulation and its stationary efflux from the cell are equal to (15,37 +/- 0.4) . 10(-6) mole/s/mg of protein and (3,01 +/- 0,8) . 10(-20) mole/s per 1 cell. respectively. The steady-state constant for glutamate synthesis from aspartic acid is equal to 0,22--0,23.

Aspartate Aminotransferases↗

PubMed1977

Interspecies comparison of cytosolic and mitochondrial aspartate aminotransferases. Evidence for a more conservative evolution of the mitochondrial isoenzyme.

The degree of structural similarity between the mitochondrial isoenzymes of aspartate aminotransferase from pig heart and chicken heart was determined by means of their immunological cross-reactivity and compared with the degree of similarity between the cytosolic isoenzymes from the same two species. Quantitative microcomplement fixation revealed a remarkable similarity of the two mitochondrial isoenzymes corresponding to an immunological distance of 104. The structures of the two cytosolic isoenzymes, on the other hand, diverge with an immunological distance of 203. The apparent conservatism of mitochondrial aspartate aminotransferase indicates additional evolutionary constraints on the structure of this organelle-confined isoenzyme.

Animals↗

PubMed1977

[Influence of Ascaridia-galli invasion on amino acid, protein and aminotransferase (GOP, GTP) levels and activities in chickens].

A negative influence of the helminths Ascaridia galli on the level of free plasma amino acids and aspartate and alanine aminotransferase activities was demonstrated in the host chick serum. Despite the above negative influence single experimental Ascaridia galli invasion failed to influence the serum protein level or weight increments in chicks. At low invasion intensity the experimental chicks were able to compensate for the pathogenic effect of the helminth Ascaridia galli, manifested by decreased amino acid and aminotransferase activity levels, provided that they were given a full-value and the chicks were kept under suitable zoohygienical conditions.

Alanine Transaminase↗

PubMed1979

Decreased aminotransferase activity of serum and various tissues in the rat after cefazolin treatment.

Treatment of rats with cefazolin in vivo significantly suppressed activity of alanine and aspartate aminotransferases in serum and in the liver, brain, kidney, and heart. Simultaneous administration of pyridoxal further reduced enzyme activity except in the liver, where there was no change. Pyridoxal 5'-phosphate partly reversed the decreased enzyme activity in the serum, liver, and kidney, but did not return it to the amount observed in the control animals; enzyme activity remained suppressed in the brain and heart. The effect of cefazolin was dose related, but there was no sex-related difference. In contrast to its action on am-notransferase activity, cefazolin elicited no effect on alkaline phosphatase (pyridoxal-5'-phosphate hydrolase) in serum or on pyruvate carboxylase in the liver, heart, and kidney. Cefazolin exposed to the hepatic microsomal mixed-function oxidase system in vitro was partly converted into metabolites that inhibited serum alanine aminotransferase activity in vitro. The latter inhibition was reversed by the addition of pyridoxal 5'-phosphate.

Alanine Transaminase↗

PubMed1979

Measurement of aspartate aminotransferase activity: effects of oxamate.

Oxamate, a potent inhibitor of lactate dehydrogenase, is shown also to inhibit aspartate aminotransferase activity, both in human serum and in purified isoenzymes of human origin. The inhibition was competitive with respect to 2-oxoglutarate for both isoenzymes. The apparent Ki was 29 mmol/L for the cytoplasmic enzyme and 17 mmol/L for the mitochondrial enzyme. Noncompetitive inhibition was found between oxamate and aspartate. At saturating concentrations of substrate (2-oxoglutarate greater than or equal to 15 mmol/L, L-aspartate greater than or equal 150 mmol/L) oxamate inhibited the mitochondrial enzyme but had less effect on the cytoplasmic isoenzyme. Oxamate at 40 mmol/L inhibited the enzyme in serum by 11 and 9% in assays containing 2-oxoglutarate at 6.7 and 15 mmol/L, respectively. This concentration of oxamate inhibited enzyme activity in serum by 5% more than did the same concentration of Cl- (itself an inhibitor). Oxamate (less than or equal to 30 mmol/L) had no measurable effect on the stability or activity of porcine malate dehydrogenase. Until the effects of its inhibitory properties are considered, addition of oxamate to suppress lactate dehydrogenase-mediated side reactions in the assay of aspartate aminotransferase cannot be recommended.

Amino Acids↗

PubMed1975

Immunochemical pattern of aspartate aminotransferase isozumes in servral rodents and in Ehrlich ascites cells (38549).

Antisera against rat liver aspartate aminotransferase (EC 2.6.1.1) isozymes were used to study the activity and immunologic pattern of these isozymes in the livers of the rat, mouse, hamster, gerbil and in Ehrlich ascites cells. A double immunodiffusion precipitin test and immunoelectrophoresis showed that, except for the gerbil, there was a pattern of identity of AAT isozymes in the presence of either the antianionic or the anticationic antisera. Although gerbil AAT isozymes are immunochemically different from those of the other rodents studied, they were inactivated by the respective antiserum in a manner similar to that observed with the other species. This may suggest that antigenic determinants at the catalytic site of each of the liver aspartate aminotransferase isozymes are least likely to change throughout the evolutionary process.

Animals↗

PubMed1979

Enzymic memory. Steady state kinetic and physical studies with ascorbate oxidase and aspartate aminotransferase.

Enzymic memory is a kinetic phenomenon observable in double displacement mechanisms. The defining feature of enzymic memory is the occurrence of different rates of transfer for a common transferable group from the substituted enzymes obtained with different donor substrates. Memory behavior was previously demonstrated for both the bovine and human liver rhodaneses (EC 2.8.1.1). Steady state kinetic tests for enzymic memory have now been done with ascorbate oxidase (EC 1.10.3.3) and aspartate aminotransferase (EC 2.6.1.1). The results were positive with ascorbate oxidase, which showed an oxygen reactivity ratio of 1:20:300 for the reduced enzymes obtained with reductate, araboascorbate, and ascorbate, respectively. Results were negative for the aminotransferase tested with the alternate donors glutamate and cysteine sulfinate, with oxaloacetate as the common acceptor. The structural basis of the ascorbate oxidase results was probed by comparison of both the ultraviolet absorption and fluorescence spectra of the oxidized enzyme with those of the reduced forms obtained with ascorbate and reductate. The results are consistent with a conformational basis for the memory phenomenon.

Animals↗

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↗

PubMed1982

The clinical chemistry of chimpanzees. I. Determination of aminotransferase baseline values for hepatitis studies.

Viral hepatitis in chimpanzees produces negligible symptomatology, and serum aminotransferase changes may be minimal. To maximize the predictive value of these determinations, which are the only serum indicators available for non-A non-B (NANB) hepatitis infection, normal ranges for aspartate and alanine aminotransferases (AST, ALT) were examined and categorized according to age and sex. Males were found to have higher values than females, and adults higher values than juveniles. The kinetic method used and the values obtained are described. Differences in methodologies and reporting units are discussed.

Animals↗

PubMed1984

"In vivo" inhibition of murine liver aspartate aminotransferase by isoniazid.

Intraperitoneal administration of isoniazid (IN), an antituberculous agent, to mice or rats at a dose of 100 mg/kg body weight resulted in remarkable and rapid inhibition of liver cytosolic aspartate aminotransferase (AAT); inhibition was less marked with other antivitamin B6 compounds; AATs in other tissues and other aminotransferases in liver were less effectively inhibited by IN. The inhibition of liver cytosolic AAT was apparently irreversible in vivo; it was reversed only a little by gel filtration and dialysis to remove excess IN in vitro, although treatment with pyridoxal phosphate or 5'-deoxypyridoxal slowly restored the full activity. Attempts to inhibit the enzyme by in vitro treatments showed that IN itself was not an effective inhibitor, while the liver extracts from IN treated mice contained some strongly inhibitory substance. In addition, the extracts were shown to contain only trace amounts of IN. These results suggest that IN is metabolized to some other form which is markedly inhibitory to murine liver cytosolic AAT, and the metabolite binds to the coenzyme moiety of enzyme in a manner not readily dissociable.

Animals↗

PubMed1978

An interlaboratory study of measurement of aspartate aminotransferase activity with use of purified enzyme materials.

The Center for Disease Control (CDC), the New York State Department of Health (NYSDH), the College of American Pathologists, and 23 manufacturers of diagnostic products participated in an interlaboratory study of aspartate aminotransferase (EC 2.6.1.1) methodologies. Six different lyophilized materials were prepared and characterized and then distributed to 293 laboratories for aspartate aminotransferase measurements. The specimens included one human serum; four catalytic concentrations of the cytoplasmic isoenzyme, two purified from human erythrocytes, and two from porcine heart; and one matrix bovine serum albumin (30 g/liter) blank. The purified isoenzymes were prepared in the matrix. We present data on Michaelis parameters (Km and Vmax), Arrhenius plots, activation with pyridoxal 5-phosphate, vial-to-vial variability, and stability on reconstitution. The 281 responses showed that most of the laboratories used NADH-detection methods (91.1%), monitored at 340 nm (79.4%), and reported results in U/liter (89.4%). The percentage of laboratories reporting use of reaction temperatures of 30 and 37 degrees C was evenly divided, i.e., 42.7 and 42%, respectively. Analytical values reported by participating laboratories were categorized by reporting temperature, instrument, and method. Results were most consistent for a selected group of laboratories that supplemented optimized reaction solutions with pyridoxal 5-phosphate.

Aspartate Aminotransferases↗

PubMedDate not supplied

[Selection of optimal conditions for measuring aspartate aminotransferase activity].

Various systems for estimation of aspartate aminotransferase activity were compare with regard to national and international recommendations. An increase of 1-aspartate concentration from 33 mM/1 to 200 mM/1 and of alpha-ketoglutarate from 6.7 mM/1 to 12 mM/1 elevated the enzymatic activity by 30-40%. Addition of pyridoxal phosphate into reaction mixture caused a decrease in the activation from 33% to 7.3%, respectively. The ratio of activation varied from 9.9% to 53.3% in the optimal test using blood serum from patients and phosphate buffer. Thus, one of requirements on evaluation of maximal aspartate aminotransferase activity and on production of reproducible results is application of optimal concentrations of reagents with addition of pyridoxal phosphate into reaction mixture.

Aspartate Aminotransferases↗