SEARCH · PubMed Health

Results for “TRANSAMINASES”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 901 records · Page 50Linked to original sources

PubMed1986

Molecular cloning of rat mitochondrial glutamic oxaloacetic transaminase mRNA and regulation of its expression in regenerating liver.

cDNA clones for rat mitochondrial glutamic oxaloacetic transaminase (mGOT) have been isolated from a rat liver cDNA library. One of the clones, designated p501, contained a cDNA insert of 1.4 kilobase pairs in length and hybridized to a mRNA of 2.4 kilobases from rat liver. We measured mGOT mRNA content in a regenerating rat liver. In a regenerating rat liver, mGOT activity was increased and reached maximum (170% of control activity) at about 48 h following the operation. Using the cDNA of mGOT, it was revealed that the increase of mGOT in the regenerating rat liver depended on its mRNA content.

Animals↗

PubMed1983

Ultrahistochemical localization of the glutamate-oxaloacetate transaminase (GOT) enzyme in hepatic and skeletal muscle cells in rat.

The ultrastructural localization of the glutamate-oxaloacetate transaminase (GOT) enzyme in hepatic and skeletal muscle cells has been studied. The GOT activity localized first on the cristae of mitochondria both in hepatic and skeletal muscle cells. Further activity of the enzyme was observed in the endoplasmic reticulum and in sarcoplasmic reticulum but not in other cell components.

Animals↗

PubMed1985

The inheritance of enzyme variants of glutamic-oxaloacetic transaminase in Paragonimus ohirai.

Lung flukes, Paragonimus ohirai, from Kinosaki, Japan, characterized by 3 electrophoretic variants, FF, FS and SS, of glutamic-oxaloacetic transaminase (GOT: EC 2.6.1.1) were crossed in the laboratory. In the case of a cross between FS and SS, a parent, FS, produced 9 SS and 16 FS clones in the offspring, numbers not significantly different from that expected (1:1) from Mendelian inheritance. From the other cross FS X FF, 20 clones originating from the respective 20 miracidia were obtained from a parent FS. The phenotype segregation ratio was 6 FF and 14 FS, which is not significantly different from Mendelian inheritance expectation. Only 3 clones were obtained from the other parent FF, but these segregated in a ratio of 2 FS: 1 FF. These breeding data indicate that the GOT isozymes of P. ohirai are controlled by 2 codominant alleles, GotF and GotS at a single locus whose products aggregate randomly, forming a dimer.

Animals↗

PubMed1977

Fluorine-19 nuclear magnetic resonance studies of effects of ligands on trifluoroacetonylated supernatant aspartate transaminase.

The selective reaction of Cys-45 and -82, on the one hand, and Cys-390, on the other, with 3-bromo-1,1,1-trifluoropropanone allows for the probing of these regions of aspartate transaminase in the absence and in the presence of enzymatic ligands by 19F nuclear magnetic resonance (NMR). The 19F chemical shifts of the resonance lines differ for the three cysteines and so does their behavior with pH changes. The resonance signals with chemical shifts at 615 and 800 Hz upfield from trifluoroacetic acid correspond to modified cysteine-82 and -45 and have tentatively been assigned in this order. The 615-Hz resonance is affected by pH changes that fit best the influence of a single ionizing residue. On the 800-Hz line, the pH changes appear to be the influence of a minimum of two ionizing residues. The 19F resonance from modified Cys-390 is pH independent in the pH range 5-9 for the pyridoxal phosphate, pyridoxamine phosphate, and apoenzyme forms of the enzyme. Occupation of the active site by a quasi-enzyme-substrate complex, trifluoromethionine pyridoxyl phosphate, affects the 19F chemical shift of modified Cys-390, making it pH dependent with a pK value of 8.4. The 19F NMR properties of the pyridoxal form of Cys-390-modified enzyme can be used to monitor some ligand interactions with the active-center region. Addition of alpha-ketoglutarate or succinate to the ketone labeled enzyme causes a decrease in the resonance line width, and titrations show that this procedure is a good method with which to study the affinity of the enzyme for these ligands. The interpretation of the chemical shift and line-width characteristics of the 19F resonance arising from Cys-390 are most consistent with a model in which the region around this residue seems to be affected by conformational changes arising from substrate binding to the active-center subsites in productive (covalent) manner. Nonproductive complexes which possess fast ligand-protein exchange, such as those between alpha-ketoglutarate or succinate with the pyridoxal phosphate form of the enzyme, may result only in a greater degree of freedom for Cys-390.

Aspartate Aminotransferases↗

PubMed1976

Nuclear magnetic resonance studies of D2O-substrate exchange reactions catalyzed by glutamic pyruvic and glutamic oxaloacetic transaminases.

Nuclear magnetic resonance studies in D2O (greater than 90%) with glutamic pyruvate transaminase (GTP) (2.6.1.2) demonstrate that this enzyme catalyzes the rapid exchange of both the alpha and beta hydrogens of L-alanine, the exchange of only one alpha hydrogen of glycine, and the beta hydrogens of pyruvate and fluoropyruvate. When the beta hydrogens of L-alanine undergo the enzyme-catalyzed exchange, the product may have 1, 2 or 3 of beta hydrogens exchanged. The exchange is stimulated by the addition of catalytic amounts of copartner of transaminations reaction. A mechanism is proposed for an extension of the conjugated system to include the alpha and beta carbons to explain the labilization of the beta hydrogens.

Alanine↗

PubMed1977

[19F]fluorine nuclear-magnetic-resonance study of the interaction of difluoro-oxaloacetate with aspartate transaminase.

Difluoro-oxaloacetate interacts with the aldimine form of aspartate transaminase to give a complex, the dissociation constant of which has been determined spectrophotometrically and by 19F n.m.r. (nuclear magnetic resonance). The 19F n.m.r. line-width-pH and chemical-shift-pH profiles of difluoro-oxaloacetate in the presence of the aldimine form of the enzyme both show inflexion points in the pH5 and pH8 regions, which may arise from variations in the binding of difluoro-oxaloacetate as specific groups on the enzyme are successively protonated. Difluoro-oxaloacetate also interacts with apoenzyme to form a complex, the dissociation constant of which was determined by 19F n.m.r. The 19F n.m.r. line-width-pH and chemical-shift-pH profiles of difluoro-oxaloacetate in the presence of apoenzyme show a single inflexion point in the region of pH8. The absence, in this case, of an inflexion in the pH5 region indicates that the latter, present in the corresponding profiles for the aldimine form of the enzyme, results from ionization of an enzyme group associated with the pyridoxal phosphate cofactor.

Aspartate Aminotransferases↗

PubMed1977

Reaction of the aminic form of aspartate transaminase with difluoro-oxaloacetate.

Addition of difluoro-oxaloacetate to the aminic form of aspartate transaminase causes a rapid shift of absorbance maximum of the enzyme from 332 nm to 328 nm, followed by a much slower shift to 360 nm corresponding to complete conversion of the aminic form of the enzyme into the aldimine form or a species with similar spectral parameters in rapid equilibrium with it. Kinetic analysis of both the initial fast reaction and the overall slow reaction by using repeated spectral scanning and stopped-flow techniques allows formulation of a basic reaction mechanism involving at least two intermediate enzyme complexes. Computer simulation of the progress curves of the initial fast reaction based on the suggested reaction mechanism gives kinetic parameters that are consistent with all the data obtained by other methods. A molecular reaction scheme involving a ketimine Schiff-base intermediate is proposed.

Aspartate Aminotransferases↗

PubMed1990

Plasma membrane fatty acid-binding protein and mitochondrial glutamic-oxaloacetic transaminase of rat liver are related.

The hepatic plasma membrane fatty acid-binding protein (h-FABPPM) and the mitochondrial isoenzyme of glutamic-oxaloacetic transaminase (mGOT) of rat liver have similar amino acid compositions and identical amino acid sequences for residues 3-24. Both proteins migrate with an apparent molecular mass of 43 kDa on SDS/polyacrylamide gel electrophoresis, have a similar pattern of basic charge isomers on isoelectric focusing, are eluted similarly from four different high-performance liquid chromatographic columns, have absorption maxima at 435 nm under acid conditions and 354 nm at pH 8.3, and bind oleate with a Ka approximately 1.2-1.4 x 10(7) M-1. Sinusoidally enriched liver plasma membranes and purified h-FABPPM have GOT enzymatic activity; the relative specific activities (units/mg) of the membranes and purified protein suggest that h-FABPPM constitutes 1-2% of plasma membrane protein in the rat hepatocyte. Monospecific rabbit antiserum against h-FABPPM reacts on Western blotting with mGOT, and vice versa. Antisera against both proteins produce plasma membrane immunofluorescence in rat hepatocytes and selectively inhibit the hepatocellular uptake of [3H]oleate but not that of [35S]sulfobromophthalein or [14C]taurocholate. The inhibition of oleate uptake produced by anti-h-FABPPM can be eliminated by preincubation of the antiserum with mGOT; similarly, the plasma membrane immunofluorescence produced by either antiserum can be eliminated by preincubation with the other antigen. These data suggest that h-FABPPM and mGOT are closely related.

Amino Acid Sequence↗

PubMed1996

Concomitant purification and characterization of malate dehydrogenase, aspartate transaminase, nucleoside diphosphate kinase and enolase from rabbit liver cytosol.

A procedure was developed for purifying the cytosolic isoforms of malate dehydrogenase, aspartate transaminase, enolase and nucleoside diphosphate kinase from a single preparation of rabbit liver. The procedure includes chromatography on reactive-dye, radial-flow columns, and elution of enzymes from columns by substrates, to obtain high yields in a minimal amount of time. The scheme avoids steps used in previous methods that are either difficult to execute in large-scale preparations, or alter the native forms of the enzymes. Examination of the purified enzymes by SDS-PAGE indicated that nearly homogeneous preparations had been obtained. The native molecular weight, subunit molecular weight, and isoelectric point(s) were determined for each enzyme. Although preparations of nucleoside diphosphate kinase purified from cytosol showed only a single band on SDS-PAGE, isoelectric focusing revealed the presence of multiple isoforms.

Animals↗

PubMed1968

Electron microscope studies of glutamic oxalacetic transaminase in rat liver cell.

Liver tissue of the rat, fixed in glutaraldehyde and formaldehyde, was incubated in a medium which consisted of 20 mML-aspartic acid, 2 mM alpha-ketoglutaric acid, 50 mM imidazole and 6 mM lead nitrate at pH 7.2-7.4. The electron-opaque precipitates, due to glutamic oxalacetic transaminase activity in liver cells, were found to be localized to the cristae and surface membranes of the mitochondria, the limiting membrane of the microbodies, and the nuclear membrane. Sucrose storage and trauma resulted in altered morphology and diminished final product intensity in mitochondria, but the microbody enzyme activity disappeared completely under these conditions. These distinctive responses of enzymatic activity are considered to indicate a difference in either the enzyme protein or its membrane attachment to these two sites. The use of a buffered dehydrating ethanol series to prepare tissue blocks for electron microscopy appeared to result in more precise intracellular localization of enzymatic reaction product.

Animals↗

PubMed1968

A biochemical and histochemical study of glutamic oxalacetic transaminase activity of rat hepatic mitochondria fixed in situ and in vitro.

Rat liver perfused in situ briefly with a glutaraldehyde-formaldehyde mixture was homogenized in isotonic sucrose. The mitochondria, isolated from a homogenate of the perfused liver by differential centrifugation, assumed a slender and compact appearance similar to those often seen in an intact cell. The glutamic oxalacetic transaminase (GOT) activity of this mitochondrial fraction survived an additional formaldehyde fixation and was studied by biochemical and histochemical methods. The biochemical assay of the enzyme activity revealed that the activity was only slightly less than that of an unfixed mitochondrial fraction. The reaction product due to mitochondrial GOT activity was found to be localized to the cristae, as had been demonstrated in an intact liver cell. GOT activity of the mitochondrial fraction isolated from fresh liver tissue homogenate in 0.25 M sucrose was inactivated readily by either glutaraldehyde or formaldehyde and was no longer demonstrable by biochemical and histochemical methods after fixation.

Animals↗

PubMed1994

Reference ranges for erythrocyte pyridoxal 5'-phosphate concentration and the erythrocyte aspartate transaminase stimulation test in lactating mothers and their infants.

We determined reference ranges for erythrocyte pyridoxal 5'-phosphate concentrations (EPLP) and erythrocyte aspartate transaminase basal activities (EASTo) and activation coefficients (alpha EAST) in lactating mothers and infants from data of mothers receiving a vitamin B-6 supplement and infants breast-fed by mothers with adequate vitamin B6 status. The mothers' vitamin B6 status was assessed on the third day postpartum (pp) (n = 91) and at 2 mo (n = 114), 4 mo (n = 117), 6 mo (n = 110), and 9 mo (n = 40) pp and that of the exclusively breast-fed infants at 2 mo (n = 90), 4 mo (n = 106), and 6 mo (n = 99). We also examined 9-mo-old infants (n = 39) who, besides breast milk, had received solids after 6 mo, and 12-mo-old infants (n = 100) who had received solids beginning at 4-6 mo and dairy products at 9 mo. Values indicating deficiency for at least two of the three indexes distinguished the 5-10% of mothers and infants with the lowest vitamin B6 status. The reference ranges for EPLP, EASTo, and alpha EAST for infants and for mothers during the first months of lactation differ from those reported earlier for adults.

Aspartate Aminotransferases↗

PubMed2000

Serum mitochondrial aspartate transaminase activity after isoflurane or halothane anaesthesia.

We examined the effect of halothane or isoflurane anaesthesia on hepatic function in 30 ASA I-III patients aged 18-70 yr undergoing lumbar discectomy. Hepatic function was assessed before anaesthesia, at the end of surgery, and at 3, 6, 24 and 48 h after surgery using routine enzyme tests of hepatic function and mitochondrial aspartate transaminase (mAST) activity. Although serum mAST activities increased after surgery in both groups of patients, these increases were statistically significantly greater in the group that received halothane. The groups were similar with regard to other tests of hepatic function. Calculation of the ratio of serum enzyme activities compared to baseline values suggested that mAST is a sensitive marker of anaesthetic-induced hepatic injury.

Adolescent↗

PubMed1983

Further evidence for a polymorphism in gametic segregation in the tetraploid treefrog Hyla versicolor using a glutamate oxaloacetic transaminase locus.

Intra- and interspecific cross combinations between the tetraploid treefrog Hyla versicolor, and between H. versicolor and the diploid treefrog Hyla chrysoscelis were performed. Progeny phenotypes resulting from these crosses were examined electrophoretically using a polymorphic glutamate oxaloacetic transaminase (GOT-1) locus, to determine the mechanism of chromosome segregation in H. versicolor, and to test theoretical expectations for isozyme expression in interspecific (2n X 4n or 4n X 2n) hybrids. In some intraspecific tetraploid crosses progeny phenotypes fit a disomic mode of segregation, whereas in other crosses a tetrasomic mode of segregation was the most probable. Additional crosses produced phenotypic ratios that conformed to either a disomic or tetrasomic mode of segregation. These results suggest that a polymorphism, with respect to segregation of gametes, exists in H. versicolor, resulting from differences in chromosome pairings during meiosis I. This polymorphism in gametic segregation occurred in both sexes. Certain crosses, however, produced phenotypic ratios that did not conform to any chromosome segregation model. Progeny phenotypes observed from most interspecific crosses conformed to expected interspecific isozyme staining intensity models. Symmetrical heterozygotes, representing either a single dose for both alternate alleles or double doses for both alternate alleles, were also observed. Such phenotypes are unexpected in triploid progeny. A null allele was postulated to account for the aberrant segregation ratios and phenotypes observed in certain intra- and interspecific crosses.

Animals↗

PubMed1978

Plasma activity of pyruvate kinase and glutamic oxalacetic transaminase as indices of myopathy in the vitamin E deficient rat.

Weanling rats were fed vitamin E deficient diets for 6 to 15 weeks and then given vitamin E orally for 4 days. Plasma obtained 1 day after the last dose was assayed for glutamic oxalacetic transaminase (GOT) and pyruvate kinase activity (PK). Administration of vitamin E resulted in reduction in activity of both enzymes. Plasma levels of alkaline phosphatase, lactic dehydrogenase, and bilirubin were unaffected by vitamin E and there was no histological evidence of liver degeneration. The number of phagocytized muscle fibers was greatly reduced by vitamin E treatment, but a substantial number of necrotic fibers were still present. With more prolonged (8 days) treatment, plasma PK and GOT levels were reduced to levels found in plasma of vitamin E replete animals and few degenerated muscle fibers could be observed. It was concluded that resolution of the necrotizing myopathy in vitamin E deficient rats is a rapid process and that the decreased activity of PK and GOT in plasma is a sensitive indicator of the resolution process. The decrease in plasma enzyme levels is an easily quantitated and reproducible biological response to vitamin E administration. Thus, this approach provides a basis for a sensitive and accurate bioassay for vitamin E activity.

Animals↗

PubMed1984

Mechanism of inactivation of pyridoxal phosphate-linked aspartate transaminase by gostatin.

The inactivation mechanism of pyridoxal phosphate-linked mitochondrial aspartate transaminase (pig heart) by gostatin (5-amino-2-carboxy-4-oxo-1,4,5,6-tetrahydropyridine-3-acetic acid), a novel amino acid produced by Streptomyces sumanensis, was investigated. Gostatin is a time-dependent inhibitor of the enzyme giving an enzyme half-life of 1.8 min at 3.1 microM (25 degrees C). The kinetic properties of the inhibitor suggest that it is a suicide substrate (mechanism-based inhibitor) of the enzyme, and the observed Ki is 59 microM and Kcat is 0.11S-1 at 25 degrees C. Incubation of the enzyme with a stoichiometric amount of the inhibitor (1 mol of inhibitor/1 mol of enzyme monomer) results in complete inactivation. Spectrophotometric titration and gel filtration experiments indicate the binding of 1 mol of gostatin with 1 mol of enzyme monomer. Gostatin serves as an efficient titrant for the enzyme. Liberation of a compound having inhibitory activity against the apo-form enzyme from the enzyme-inhibitor complex under denaturing conditions suggests irreversible modification of the cofactor.

Amino Acids, Dicarboxylic↗

PubMedDate not supplied

The genetics of glutamate oxaloacetate transaminase in Drosophila melanogaster.

A survey of 29 laboratory populations of Drosophila melanogaster for glutamate oxaloacetate transaminase (GOT) variation revealed that the Got-1 locus was polymorphic in three stocks recently collected from nature. The Got-1 locus was fixed for the same allozyme in the remaining 26 laboratory populations. Testcross matings to multiply marked stocks established that Got-1 is located at 4.8 centimorgans on chromosome 2.

Animals↗

PubMedDate not supplied

Linkage of the equine serum esterase (Es) and mitochondrial glutamate oxaloacetate transaminase (GOTM) loci. A horse-mouse homology.

Three previously described electrophoretic phenotypes of mitochondrial glutamate oxaloacetate transaminase (GOTM) in horse leukocytes are shown to be controlled by two codominant alleles at a single autosomal locus. The GOTM locus is linked to the serum esterase locus (Es), as no recombination between these loci was observed among 16 informative offspring in one sire family. The results assign GOTM to equine linkage group (LG) II. The hypothesis that a part of LG II (e-Es) shares homologies with mouse chromosome 8 is thus confirmed, as the murine homologue of GOTM is located within the cluster of esterase loci on chromosome 8. The assumed homology also involves rabbit LG VI, rat LG V, and human chromosome 16. The observation is a striking example of the conservation of linkage relationships between mammalian species.

Animals↗