Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.6.1.2 (alanine aminotransferase)
 26,722 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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.
 ...
PMID:Nuclear magnetic resonance studies of D2O-substrate exchange reactions catalyzed by glutamic pyruvic and glutamic oxaloacetic transaminases. 99 42

The hydrogen exchange at the Beta-carbon of L-alanine, L-glutamate and L-asparate with water has been examined during transamination catalyzed by glutamic-oxaloacetic transaminase and by glutamic-pyruvic transaminase. A significant hydrogen exchange at the Beta-carbon has been demonstrated during incubation of L-[3-3H]alanine + glutamic-pyruvic transaminase, L-[3-3H]alanine + alpha-oxo-glutarate + glutamic-pyruvic transaminase, L-[3-3H]glutamate + glutamic-oxaloacetic transaminase, L-[3-3H]glutamate + oxaloacetate +glutamic-oxaloacetic transaminase, and L-[3-3H]glutamate + pyruvate + glutamic-pyruvic transaminase as shown by the appearance of 3H2O. No hydrogen exchange at the Beta-carbon of L-glutamate occurred during incubation of L-[3-3H]-glutamate with glutamic-pyruvic transaminase alone. The hydrogen exchaned at the Beta-carbon of L-glutamate coincides with transamination as demonstrated by nuclear magnetic resonance studies of 2H2O-L-glutamate exchange during transamination by glutamic-oxaloacetic transaminase and glutamic-pyruvic transaminase. No hydrogen exchange at the Beta-carbon occurred during transamination of L-aspartate by glutamic-oxaloacetic transaminase as shown by nuclear magnetic resonance spectroscopy and confirmed by nuclear magnetic resonance simulation studies. The results are discussed with special reference to the different equilibria between the pyridoxal form and the pyridoxamine form of glutamic-oxaloacetic transaminase and of glutamic-pyruvic transaminase.
 ...
PMID:Hydrogen exchane at the beta-carbon of amino acids during transamination. 120 22

Pulsed Fourier transform proton magnetic resonance spectroscopy was used to study the glutamate-alanine transaminase-catalyzed incorporation of deuterium from solvent deuterium oxide into the alpha and beta positions of L-alanine. It was found that the beta proton resonance signal initially disappears slightly faster than the signal due to the alpha proton, but whereas the alpha proton signal decays exponentially, that due to the beta proton signal does not. Eventually, the rate of decrease of the alpha proton signal becomes greater than that for the beta proton. This change in the relative rates is ascribed to a deuterium isotope effect upon substitution of an alpha proton by a deuteron. Furthermore, as deuterium begins to replace hydrogen, two classes of alanine become distinguishable, i.e. alanine which contains deuterium in the alpha position and hydrogen in the beta position, and alanine which contains hydrogen in the alpha position and deuterium in the beta position. Thus, removal of all 3 beta protons is not contingent upon loss of an alpha proton from the same molecule. The two classes of deuterated alanine may conceivably arise by a scrambling mechanism in which protons are transferred from the alpha to the beta position and vice versa. Present evidence excludes this scramblong mechanism and leads to the conclusion that deuterium incorporation into L-alanine involves, (a) the reversible enzymatic conversion of the classical ketimine enzymes intermediate to an enaminetype structure, and (b) considerable conservation of label during the prototropic shift from the alpha carbon of L-alanine to the C4-position of pyridoxal 5'-phosphate. It is also postulated that alanine binds at the active site in such a way as to bring the beta protons into close contact with a basic group on the enzyme surface. This group is distinct from that used in abstraction of an alpha proton. The beta protons of glutamate are not enzymatically removed; presumably glutamate binds in such a way that the beta protons cannot effectively interact with an enzyme base. Similar studies were carried out on soluble glutamate-aspartate transaminase; no evidence was found for significant enzyme-catalyzed deuterium incorporation into the beta position of L-glutamate, L-aspartate, and L-alanine.
 ...
PMID:Proton magnetic resonance studies of glutamate-alanine transaminase-catalyzed deuterium exchange. Evidence for proton conservation during prototropic transfer from the alpha carbon of L-alanine to the C4-position of pyridoxal 5'-phosphate. 124 68

Ubiquinol-1 in aerated aqueous solution inactivates several enzymes--alanine aminotransferase, alkaline phosphatase, Na+/K(+)-ATPase, creatine kinase and glutamine synthetase--but not isocitrate dehydrogenase and malate dehydrogenase. Ubiquinone-1 and/or H2O2 do not affect the activity of alkaline phosphatase and glutamine synthetase chosen as model enzymes. Dioxygen and transition metal ions, even if in trace amounts, are essential for the enzyme inactivation, which indeed does not occur under argon atmosphere or in the presence of metal chelators. Supplementation with redox-active metal ions (Fe3+ or Cu2+), moreover, potentiates alkaline phosphatase inactivation. Since catalase and peroxidase protect while superoxide dismutase does not, hydrogen peroxide rather than superoxide anion seems to be involved in the inactivation mechanism through which oxygen active species (hydroxyl radical or any other equivalent species) are produced via a modified Haber-Weiss cycle, triggered by metal-catalyzed oxidation of ubiquinol-1. The lack of efficiency of radical scavengers and the almost complete protection afforded by enzyme substrates and metal cofactors indicate a 'site-specific' radical attack as responsible for the oxidative damage.
 ...
PMID:Enzyme inactivation by metal-catalyzed oxidation of coenzyme Q1. 135 46

We determined transaminases in human blood serum with an amperometric glutamate biosensor. The probe was a hydrogen peroxide sensor assembled with appropriate selective membranes to enhance the probe specificity and lifetime. Calibration curves of glutamate were linear in the range 1-1000 mumol/L, with a response time of < 1 min. This probe was subsequently applied to the measurement of activities of aspartate and alanine aminotransferases in human sera. Analytical recovery studies demonstrated the suitability of the glutamate sensor by measuring 91-99% of added glutamate, 92-106% of added aspartate aminotransferase, and 101-105% of added alanine aminotransferase. Transaminase activity measured in 80 sera correlated well with results obtained with a spectrophotometric procedure.
 ...
PMID:Analysis for transaminases in serum with an amperometric glutamate electrode. 135 81

Many modifications of the UW solution have been reported to yield successful results in rat liver preservation and transplantation. One solution used histidine, in combination with lactobionate (HL-I), and gave superior preservation of the rat liver when compared with the UW solution. In this study we have compared the HL-I solution with 90 mM histidine, HL-II solution with 30 mM histidine, and the UW solution in dog liver preservation and transplantation. Dog livers were preserved for 48 hr in one of the three solutions and transplanted. The peak AST and ALT values were highest in livers preserved in HL-I, intermediate in UW solution, and lowest in HL-II. However, there were no significant differences among survival rates (average 5-7 days per group), posttransplant serum concentration of liver enzymes (AST, ALT, LDH, and alk-phos), clotting factors (PT and PTT), bilirubin, and fibrinogen concentration for each group. Dogs were sacrificed or died within 5-7 days due to rejection in nonimmunosuppressed dogs. Also, rat livers were preserved in the HL-II solution or in a solution in which histidine was replaced by isoleucine (IL-I). Isoleucine is an amino acid with a molecular mass similar to that of histidine, but is not as good a hydrogen ion buffer as histidine at the pH used for liver preservation (7.4). The buffer capacity of the IL-I solution was similar to the UW solution, but about one-half as much as the HL-II solution. Rats receiving a liver preserved for 30 hr in HL-II or IL-I were 100% viable. Rats receiving a liver preserved for 40-44 hr in HL-II or IL-I showed less survival (33% and 25%, respectively). This shows that histidine can be effectively replaced by isoleucine in a preservation solution and gives equivalent preservation results. Thus, the mechanism of improvement of liver preservation with histidine is not due to its action as a hydrogen ion buffer. These studies show that, although the HL solutions are superior for preservation of the rat liver, they are not superior to the UW solution for preservation of the dog liver. However, as others have shown in the rat liver transplant model, a simplified UW solution (HL-II) appears effective in dog liver preservation. The dog liver transplant model remains a more appropriate model for testing new preservation solutions prior to initiation of clinical trials.
 ...
PMID:A comparison of histidine-lactobionate and UW solution in 48-hour dog liver preservation. 141 52

The complete amino acid sequence of human liver cytosolic alanine aminotransferase (GPT) (EC 2.6.1.2) is presented. Two primary sets of overlapping fragments were obtained by cleavage of the pyridylethylated protein at methionyl and lysyl bonds with cyanogen bromide and Achromobacter protease I, respectively. Isolated peptides were analyzed with a protein sequencer or with a plasma desorption time of flight mass spectrometer and placed in the sequence on the basis of their molecular mass and homology to the sequence of rat GPT. The protein was found to be acetylated at the amino terminus and contained 495 amino acid residues. The Mr of the subunit was calculated to be 54,479, which was in good agreement with a Mr of 55,000 estimated by SDS-PAGE, and also indicated that the active enzyme with a Mr of 114,000 was a homodimer composed of two identical subunits. The amino acid sequence is highly homologous to that of rat GPT (87.9% identity) recently determined [Ishiguro, M., Suzuki, M., Takio, K., Matsuzawa, T., & Titani, K. (1991) Biochemistry 30, 6048-6053]. All of the crucial amino acid residues are conserved in human GPT, which seem to be hydrogen bonding to pyridoxal 5'-phosphate in rat GPT by the sequence homology to other alpha-aminotransferases with known tertiary structures.
 ...
PMID:Complete amino acid sequence of human liver cytosolic alanine aminotransferase (GPT) determined by a combination of conventional and mass spectral methods. 193 70

The complete amino acid sequence of rat liver cytosolic alanine aminotransferase (EC 2.6.1.2) is presented. Two primary sets of overlapping fragments were obtained by cleavage of the pyridylethylated protein at methionyl and lysyl bonds with cyanogen bromide and Achromobacter protease I, respectively. The protein was found to be acetylated at the amino terminus and contained 495 amino acid residues. The molecular weight of the subunit was calculated to be 55,018 which was in good agreement with a molecular weight of 55,000 determined by SDS-PAGE and also indicated that the active enzyme with a molecular weight of 114,000 was a homodimer composed of two identical subunits. No highly homologous sequence was found in protein sequence databases except for a 20-residue sequence around the pyridoxal 5'-phosphate binding site of the pig heart enzyme [Tanase, S., Kojima, H., & Morino, Y. (1979) Biochemistry 18, 3002-3007], which was almost identical with that of residues 303-322 of the rat liver enzyme. In spite of rather low homology scores, rat alanine aminotransferase is clearly homologous to those of other aminotransferases from the same species, e.g., cytosolic tyrosine aminotransferase (24.7% identity), cytosolic aspartate aminotransferase (17.0%), and mitochondrial aspartate aminotransferase (16.0%). Most of the crucial amino acid residues hydrogen-bonding to pyridoxal 5'-phosphate identified in aspartate aminotransferase by X-ray crystallography are conserved in alanine aminotransferase. This suggests that the topology of secondary structures characteristic in the large domain of other alpha-aminotransferases with known tertiary structure may also be conserved in alanine aminotransferase.
 ...
PMID:Complete amino acid sequence of rat liver cytosolic alanine aminotransferase. 204 42

The pharmacology, pharmacokinetics, clinical efficacy, adverse effects, and dosage and administration of omeprazole are reviewed. Omeprazole, a substituted benzimidazole, has a unique site and mechanism of action because it inhibits the proton pump--i.e., hydrogen, potassium adenosine triphosphatase (H+,K+-ATPase)--and consequently blocks the final common step in the gastric acid secretory pathway. Omeprazole inhibits basal and histamine-, gastrin- and pentagastrin-stimulated gastric hydrochloric acid secretion. It produces a dose-dependent reduction in gastric acidity, gastric acid output, and gastric juice volume and has variable effects on pepsin secretion. Omeprazole has no documented effect on esophageal motility or lower esophageal sphincter pressure. Omeprazole is variably absorbed from the gastrointestinal tract, and food appears to decrease the rate, but not the extent, of drug absorption. The drug is approximately 95% bound to plasma proteins and is metabolized to inactive components that are enterohepatically or renally eliminated. Omeprazole is more effective (in most studies) than H2-receptor antagonists in treating duodenal ulcer, at least as effective in treating benign gastric ulcer, and more effective in treating reflux esophagitis. Omeprazole has been used successfully in patients with Zollinger-Ellison syndrome refractory to treatment with H2-receptor antagonists. Gastrointestinal complaints (nausea and diarrhea) are the most commonly reported adverse effects associated with omeprazole therapy. The most frequently reported laboratory abnormality occurring with omeprazole use is elevation of serum aspartate aminotransferase and alanine aminotransferase concentrations. Omeprazole will serve a valuable role in the management of gastrointestinal tract ulcers and hypersecretory conditions.
 ...
PMID:Therapeutic evaluation of omeprazole. 306 85

The aim of this study was tracing of changes in the activity of glutathione peroxidase (GSHPx), glutathione transferase (GSH S-Tr), aspartate aminotransferase (AspAT) and alanine aminotransferase (A1AT) in the brain as a result of diet enrichment with antioxidants: selenium (Se), vitamin E and vitamin B15 (pangamic acid). The experiment was carried out on Wistar rats with initial body weight 150 g. Following prolonged enrichment of diet with Se (0.1 ppm of sodium selenite), vitamin E (6 mg/100 g of diet) and vitamin B15 (2.5 mg/100 g of diet) the following results were obtained. The activity of GSHPx in brain microsomes was not changed after one year of vitamin E administration when it was measured against hydrogen hydroxide and against cumene hydrochloride; vitamin E administration increased the activity of GSH S-Tr in the cytoplasmic fraction of brain cells. Diet enrichment with selenium increased after 12 and 18 months the activity of GSHPx measured against both substrates, and GSH S-Tr activity increased considerably. Presence of vitamin B15 in diet reduced GSHPx activity after one-year or longer administration, after 18 months the activity of GSH S-Tr was reduced also. No changes were noted in the activity of AspAT and A1AT.
 ...
PMID:The effect of long-term enrichment of diet with selenium, vitamin E and B15 on the activity of certain enzymes in rat brain. 345 69


1 2 3 4 5 6 7 8 9 10 Next >>