Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “TRANSAMINASES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 199 records · Page 11Linked to original sources
PubMed1987

Localization of L-glutamate decarboxylase and GABA transaminase immunoreactivity in the sympathetic ganglia of the rat.

The location of L-glutamate decarboxylase and gamma-aminobutyrate (GABA)-transaminase immunoreactivity in the superior cervical ganglion and in the coeliac-superior mesenteric ganglion complex of the rat was studied by an indirect immunofluorescence method and by immunoelectron microscopy, with specific antisera raised in rabbits against the corresponding enzymes. In light microscopy, several glutamate decarboxylase- or GABA-transaminase-immunoreactive principal nerve cells were detected in the superior cervical ganglion and coeliac-superior mesenteric ganglion complex. In addition, numerous small cells in both the superior cervical ganglion and coeliac-superior mesenteric ganglion complex showed intense immunoreactivity to glutamate decarboxylase or GABA-transaminase. The small cells were 10-20 micron in diameter and resembled in size and morphology the small intensely fluorescent cells. In consecutive sections, the small glutamate decarboxylase-immunoreactive cell clusters also showed immunoreactivity to tyrosine hydroxylase, suggesting that these cells contain the enzymes for both GABA and catecholamine synthesis. In the superior cervical ganglion and in the coeliac-superior mesenteric ganglion complex, GABA-transaminase immunoreactivity was also localized in fibre-like processes around and between the principal nerve cells, in nerve trunks traversing the ganglia, and around or in close contact with ganglionic blood vessels. Furthermore, GABA-transaminase immunoreactivity was observed in fibre-like structures close to the capsule of the ganglia. Division of the preganglionic nerve trunk of the superior cervical ganglion caused no detectable change in GABA-transaminase immunoreactivity in the ganglion. In immunoelectron microscopy of the superior cervical ganglion, GABA-transaminase immunoreactivity was localized in nerve fibres in association with neurotubules. A large number of GABA-transaminase labelled principal nerve cells were detected, containing immunoreactivity evenly distributed in their cytoplasm. GABA-transaminase immunoreactivity was also observed in satellite cells and their processes in the superior cervical ganglion. The present immunocytochemical results provide evidence that the rat sympathetic ganglia contain an intrinsic neuronal system showing histochemical markers for GABA synthesis and inactivation, but its functional role in the modulation of ganglionic neurotransmission remains to be established.

4-Aminobutyrate Transaminase↗
PubMed1982

Analysis of an avtA::Mu d1(Ap lac) mutant: metabolic role of transaminase C.

Escherichia coli can synthesize alpha-ketoisovalerate, the precursor of valine, leucine, and pantothenate, by three routes: anabolically via dihydroxyacid dehydrase and catabolically via both the branched-chain amino acid transaminase (transaminase B) and the alanine-valine transaminase (transaminase C). An E. coli K-12 mutant devoid of transaminase C (avtA) was isolated by mutagenizing an isoleucine-requiring strain devoid of transaminase B (ilvE::Tn5) with Mu d1(Ap lac) and selecting for valine-requiring derivatives which were ampicillin resistant, Lac+, able to crossfeed an ilvD mutant, and unable to grow on alpha-ketoisovalerate in place of valine. Strains defective in one, two, or all three alpha-ketoisovalerate metabolic enzymes were constructed, and their properties were analyzed. The data indicated that avtA is the structural gene for transaminase C, that transaminase C is a single enzyme species, and that the sole pathway for pantothenate biosynthesis is from alpha-ketoisovalerate. The data further showed that isoelectric inhibits the transaminase B-catalyzed deamination of valine in vivo.

Aminobutyrates↗
PubMed1996

Cloning and expression of a rat kidney cytosolic glutamine transaminase K that has strong sequence homology to kynurenine pyruvate aminotransferase.

An alpha-keto acid-dependent cysteine S-conjugate beta-lyase of rat kidney was identified as cytosolic glutamine transaminase K by Stevens et al. (J. Biol. Chem. 261, 15529-15537, 1986). Subsequently, a rat kidney protein with both glutamine transaminase K- and cysteine S-conjugate beta-lyase activities was cloned and sequenced by Perry et al. (Mol. Pharmacol. 43, 660-665, 1993). This protein was later shown to be identical with kynurenine pyruvate aminotransferase (Mosca et al., FEBS Lett. 353, 21-24, 1994). Thus, kynurenine pyruvate aminotransferase possesses both glutamine transaminase K- and cysteine S-conjugate beta-lyase-type activities. We have also cloned a cytosolic glutamine transaminase K from a rat kidney cDNA library and expressed the full-length clone in COS1 cells. The transfected cells exhibit marked increases in activities of both glutamine transaminase K and cysteine S-conjugate beta-lyase. The enzyme cloned in the present work is a homodimer. Each subunit has a molecular mass of 45.8 kDa and contains 426 amino acid residues. The sequence of cytosolic glutamine transaminase K obtained in the present work has strong similarities to other aminotransferases, including >90% identity with kynurenine pyruvate aminotransferase. Our preparation of purified rat kidney cytosolic glutamine transaminase K possesses some kynurenine pyruvate aminotransferase activity. Thus, rat kidney cytosol possesses at least two distinct enzymes that catalyze glutamine transaminase K/cysteine S-conjugate beta-lyase/kynurenine pyruvate aminotransferase reactions. The present work underscores the difficulties associated with characterizing aminotransferases with overlapping specificities.

Amino Acid Sequence↗
PubMed1994

Oral lichen planus and chronic liver disease: a clinical and morphometric study of the oral lesions in relation to transaminase elevation.

Serum transaminase levels (serum glutamic-oxaloacetic transaminase or serum glutamic-pyruvic transaminase) were found to be altered in 40 (21.39%) of 187 patients with oral lichen planus. The patients with oral lichen planus who had altered transaminase levels were on average older than those without liver disorders and exhibited a higher percentage of erosive lesions (p < 0.05) and tongue involvement. Histologically, no statistically significant differences were noted in the extension of inflammatory infiltration or in connective tissue density; nevertheless, the latter was greater in patients without altered transaminase levels. Finally, among those patients with altered liver test results and erosive lichen planus, serum glutamic-oxaloacetic transaminase and serum glutamic-pyruvic transaminase levels were found to be higher than levels in those patients without erosions. This indicates that behavior of the oral lesions is more aggressive as the degree of liver alteration increases. We emphasize that of the 40 patients with altered transaminase levels (all later proved to reflect chronic hepatitis through complementary diagnostic methods), 28 had hepatitis C virus infection.

Alanine Transaminase↗
PubMed2002

Role of hepatitis C virus genotype in the development of severe transaminase elevation after the introduction of antiretroviral therapy.

OBJECTIVE: To assess the role of different hepatitis C virus (HCV) genotypes in the development of transaminase elevation after treatment with highly active antiretroviral therapy (HAART). DESIGN: Retrospective cohort study at one referral HIV outpatient clinic. METHODS: HCV genotype was determined in plasma samples from all consecutive HCV-HIV coinfected patients initiating HAART between March 1998 and January 2000. Clinical and laboratory data were recorded during the following 9 months. Severe transaminase elevation was defined as > or = fivefold increase over upper normal limits (AIDS Clinical Trials Group grades 3 or 4) when baseline alanine transaminase (ALT) and aspartate transaminase (AST) values were normal, and as > or = 3.5-fold increase above baseline ALT and AST values if they were abnormal. RESULTS: Twelve of 70 subjects (17%) developed severe transaminase elevation. Their HCV genotypes were distributed as follows: type 1, 5/39 (13%); type 2, 0/3 (0%); type 3, 7/21 (33%); and type 4, 0/7 (0%). The incidence of severe transaminase elevation was significantly higher among subjects with HCV genotype 3 (HCV-3) compared with those with non-type 3 (OR, 4.4 [95%CI, 1.2-16.1]; P =.02). In the multivariate analysis, HCV-3 remained associated with severe transaminase elevation when adjusted for baseline HCV viral load and degree of immune recovery seen during follow-up evaluation. CONCLUSIONS: HCV-3 is an independent risk factor for developing severe transaminase elevation after HAART. HCV genotyping before initiating antiretroviral therapy may be useful for assessing the risk of hepatotoxicity and for choosing the most appropriate drugs to prescribe for HIV-HCV coinfected patients. Given that the best response to interferon plus ribavirin occurs in patients with HCV-3, treatment should be specially encouraged in coinfected persons carrying HCV-3.

Adult↗
PubMed1991

Cytosolic L-alanine:4,5-dioxovalerate transaminase differs from the mitochondrial form.

L-Alanine:4,5-dioxovalerate transaminase was detected in the kidney cytosolic fraction with a lower specific activity than the mitochondrial enzyme. The enzyme was purified from the cytosol to homogeneity with a yield of 32%, and comparative analysis with the mitochondrial form was performed. Both forms of the enzyme have identical pH and temperature optima and also share common antigenic determinants. However, differences in their molecular properties exist. The molecular mass of the native cytoplasmic enzyme is 260 kDa, whereas that of the mitochondrial enzyme is 210 kDa. In addition, the cytoplasmic L-alanine: 4,5-dioxovalerate transaminase had a homopolymeric subunit molecular mass of 67 kDa compared to a subunit molecular mass of 50 kDa for the mitochondrial L-alanine:4,5-dioxovalerate transaminase. This is the first report of two forms of L-alanine:4,5-dioxovalerate transaminase. The different responses of cytosolic and mitochondrial L-alanine:4,5-dioxovalerate transaminases to hemin supplementation both in vitro and in vivo was demonstrated. Maximum inhibition of mitochondrial L-alanine:4,5-dioxovalerate transaminase activity was demonstrated with hemin injected at a dose of 1.2 mg/kg body mass, whereas the same dose of hemin stimulated the cytosolic enzyme to 150% of the control. A one-dimensional peptide map of partially digested cytosolic and mitochondrial L-alanine:4,5-dioxovalerate transaminase shows that the two forms of the enzymes are structurally related. Partial digestion of the cytosolic form of the enzyme with papain generated a fragment of 50 kDa which was identical to that of the undigested mitochondrial form (50 kDa). Moreover, papain digestion resulted in a threefold increase in cytosolic enzyme activity over the native enzyme, and such enhancement was comparable to the activity of the mitochondrial form of the enzyme. Therefore, we conclude that the cytosolic form of L-alanine: 4,5-dioxovalerate transaminase is different from the mitochondrial enzyme. Furthermore, immunoblot analysis indicated that the mitochondrial enzyme has antigenic similarity to the cytosolic enzyme as well as to the papain-digested cytosolic enzyme 50-kDa fragment.

Animals↗
PubMed1981

Sulfation of lithocholate as a possible modifier of chenodeoxycholic acid-induced elevations of serum transaminase in patients with gallstones.

Chenodeoxycholic acid (CDC), through its metabolite, lithocholic acid (LC), is hepatotoxic in certain species. The cause of elevations of serum transaminase in 25% of humans ingesting CDC, however, is unknown, but also may be due to LC. Because efficient hepatic sulfation of LC may protect against hepatic injury, the aim of this study was to determine if sulfation of LC might modify CDC-induced elevations of transaminase. Pretreatment sulfation fraction (SF) was estimated in 63 randomly selected patients with gallstones in a double-blind randomized trial of CDC, 750 mg/d, 375 mg/d, or placebo; in 27 of these, SF was repeated at 1 or 2 yr. In four other patients, the SF was measured at 2 yr only. Serum glutamic oxaloacetic transaminase and serum glutamic pyruvic transaminase were determined monthly for 3 mo and then every 3 or 4 mo; an elevation of transaminase was defined as > 150% of the normal upper limit in asymptomatic patients. 10 muCi of (3)H-glyco-LC (sp act 84 mCi/mol) was ingested 10-12 h before fasting duodenal biliary drainage. Bile acids in bile were separated by thin-layer chromatography. The SF was estimated as a percentage of total radioactivity (scintillation counting) in sulfated glyco-LC. The standard deviation for replicate SF determinations (n = 311) was 2.1% The pretreatment SF (mean 60.7+/-1.7 SEM) correlated inversely with age (r = 0.336, P < 0.005) and directly with the obesity index (r = 0.495, P > 0.001), but was independent of sex. The SF, remeasured at 1 or 2 yr, did not change significantly with time or CDC. Among CDC-treated patients, elevations of transaminase occurred in 75% of patients with a SF < 45% vs. 11% with a SF > 45% (P < 0.001). In conclusion, a SF < 45% occurred in patients with gallstones who had a high probability of developing elevated serum transaminase when treated with CDC. Thus, sulfation of lithocholate may modify CDC-induced elevations of serum transaminase.

Aged↗
PubMed1987

[Alanine and aspartate transaminase and acid and alkaline phosphatase activities in the blood serum in relation to the protein and energy levels in the pigs' feeds].

The activity of alanine and asparagine transaminase and of acid and basic phosphatase was studied in blood serum of 72 porkers of the Polish large-white breed, fed with PT-2 feeds of various protein and energy levels. It was found that the activity of both transaminases in blood serum depended on the protein-energy level of the diet. The activity of transaminases was not found to increase at the protein content compatible with the standard and at increased energy value of the feeds, whereas the same protein level and decreased energy amount caused a decrease in the activity of alanine and asparagine transaminase. At a decreased protein content in the diet the activity of transaminases in plasma was lower than in the porkers on a diet containing protein according to the standard. An increased amount of energy with a decreased protein content in the diet did not affect the activity of asparagine transaminase but slightly stimulated alanine transaminase, whereas a decrease in the amount both of energy and protein in the diet caused an increase in the activity of both transaminases. Acid and basic phosphatase were not adequate indices of changes in the organism of the porkers in relation to the protein-energy level of their diet.

Acid Phosphatase↗
PubMed1977

Two omega-amino acid transaminases from Bacillus cereus.

Bacillus cereus strain K-22 produced two distinct omega-amino acid transaminases, one catalyzing the transamination between beta-alanine and pyruvic acid and the other that between gamma-aminobutyric acid and alpha-ketoglutaric aic. The two enzymes were partially purified and separated from each other by various chromatographies. beta-Alanine:pyruvic acid transaminase and gamma-aminobutyric acid:alpha-ketoglutaric acid transaminase were induced by the addition of beta-alanine and gamma-aminobutyric acid, respectively, to the growth medium. beta-Alanine transaminase showed an optimum pH of 10.0 and optimum temperature of 35 degrees C, and its Km values for beta-alanine and pyruvic acid were both 1.1 mM. gamma-Aminobutyric acid, epsilon-aminocaproic acid, 2-aminoethylphosphonic acid, and propylamine showed about 30-40% of the activity of beta-alanine as amino donors, and oxalacetic acid was as good an amino acceptor as pyruvic acid. The optimum pH and temperature of gamma-aminobutyric acid transaminase were 9.0 and 50 degrees C, respectively, and its Km value for gamma-aminobutyric acid was 2.8 mM, while that for alpha-ketoglutaric acid was 2.3 mM. gamma-Aminobutyric acid and delta-aminovaleric acid were good amino donors but other omega-amino acids were virtually inactive with gamma-aminobutyric acid transaminase; alpha-ketoglutaric acid, and to a lesser extent glyoxylic acid, were active amino acceptors. Sulfhydryl reagents specifically activated gamma-aminobutyric acid transaminase.

4-Aminobutyrate Transaminase↗
PubMed2003

Purification, characterization, and molecular cloning of a novel amine:pyruvate transaminase from Vibrio fluvialis JS17.

A transaminase from Vibrio fluvialis JS17 showing activity toward chiral amines was purified to homogeneity and its enzymatic properties were characterized. The transaminase showed an apparent molecular mass of 100 kDa as determined by gel filtration chromatography and a subunit mass of 50 kDa by MALDI-TOF mass spectrometry, suggesting a dimeric structure. The enzyme had an isoelectric point of 5.4 and its absorption spectrum exhibited maxima at 320 and 405 nm. The optimal pH and temperature for enzyme activity were 9.2 and 37 degrees C, respectively. Pyruvate and pyridoxal 5'-phosphate increased enzyme stability whereas (S)-alpha-methylbenzylamine reversibly inactivated the enzyme. The transaminase gene was cloned from a V. fluvialis JS17 genomic library. The deduced amino acid sequence (453 residues) showed significant homology with omega-amino acid:pyruvate transaminases (omega-APT) from various bacterial strains (80 identical residues with four omega-APTs). However, of 159 conserved residues in the four omega-APTs, 79 were not conserved in the transaminase from V. fluvialis JS17. Taken together with the sequence homology results, and the lack of activity toward beta-alanine (a typical amino donor for the omega-APT), the results suggest that the transaminase is a novel amine:pyruvate transaminase that has not been reported to date.

Amino Acid Sequence↗
PubMed1982

GABA-transaminase in the basal ganglia: a pharmacohistochemical study.

A pharmacohistochemical procedure to demonstrate histochemically those cells with the ability to synthesize the GABA-metabolizing enzyme GABA-transaminase has been applied to determine the localization of this enzyme in the basal ganglia. In normal, pharmacologically unmanipulated animals, strong GABA-transaminase activity is present throughout the neuropil in many nuclei of the basal ganglia. The striatum, globus pallidus, entopeduncular nucleus, subthalamic nucleus and substantia nigra are all heavily stained. White matter such as the corpus callosum and internal capsule are unstained. Pretreatment of rats with the irreversible GABA-transaminase inhibitor ethanolamine-O-sulfate resulted in a marked reduction in the general neuropil staining. At a suitable post-injection survival time, cells which had synthesized new GABa-transaminase molecules could be detected. Small, positive neurons were present in the striatum and entopeduncular nucleus, while the globus pallidus, substantia nigra zona reticulata, and the ventral pallidal region contained many large, intensely GABA-transaminase-positive neurons. The results indicate that much of the GABA-transaminase in the basal ganglia is neuronal in origin. The relationship of GABA-transaminase to GABA neurons is discussed.

4-Aminobutyrate Transaminase↗
PubMed1979

Microbial transaminase activities and their relationship with bovine rumen metabolites.

Two each adult male crossbred cattle and murrah buffalo were fed a diet of alfalfa hay, chopped wheat straw, and concentrate mixture. Total rumen transaminase activity of cattle was higher than that of buffalo. Rumen protozoal fractions showed higher total transaminase activity than bacterial fractions in both ruminant species. Besides generally studied glutamate oxalacetate transaminase and glutamate pyruvate transaminase, a large number of other microbial transaminases also have been detected in the rumen of both the ruminant species. Bacterial fractions of rumen liquor were devoid of transaminases utilizing tryptophan, threonine, and lysine as their substrates. Ruminal ammonia and nonprotein nitrogen were correlated positively with microbial transaminases in both species. Transamination reactions may be important for assimilation of ruminal ammonia to cellular proteins.

Alanine Transaminase↗
PubMed2003

Simultaneous synthesis of enantiomerically pure (S)-amino acids and (R)-amines using coupled transaminase reactions.

For the simultaneous synthesis of enatiomerically pure (S)-amino acids and (R)-amines from corresponding alpha-keto acids and racemic amines, an alpha/omega-transaminase coupled reaction system was designed using favorable reaction equilibrium shift led by omega-transaminase reaction. Cloned tyrB, aspC and avtA, and omegataA were co-expressed in E. coli BL21(DE3) using pET23b(+) and pET24ma, respectively. The coupled reaction produced the (S)-amino acids with 73-90% (> 99% ee(S)) of conversion yield and resolved the racemic amines with 83-99% ee(R) for 5 to 10 hours. In designing the coupled reactions in the cell, alanine and pyruvate were efficiently used in the cell as an amine donor for the alanine transaminase and an amino acceptor for the omega-transaminase, respectively, resulting in an alanine-pyruvate shuttling system. The common problem of the low equilibrium constant of the alpha-transaminase can be efficiently overcome by the coupling with the omega-transaminase. However, overcoming the product inhibition of omega-transaminase by the ketone by-product and increasing the decarboxylation rate of the oxaloacetate produced during the transaminase reaction become barriers to further improving the overall reaction rate and the yield of the coupled reactions.

Amines↗
PubMed1991

Glutamine transaminase K and cysteine S-conjugate beta-lyase activity stains.

An activity stain to detect glutamine transaminase K subjected to nondenaturing polyacrylamide gel electrophoresis (ND-PAGE) was developed. The gel is incubated with a reaction mixture containing L-phenyl-alanine, alpha-keto-gamma-methiolbutyrate (alpha KMB), glutamate dehydrogenase, phenazine methosulfate (PMS) and nitroblue tetrazolium (NBT). Glutamine transaminase K catalyzes a transamination reaction between phenylalanine and alpha KMB. The resultant methionine is a substrate of glutamate dehydrogenase. The NADH formed in the oxidative deamination of methionine reacts with PMS and NBT to form a blue band on the surface of the gel coincident with glutamine transaminase K activity. Cysteine S-conjugate beta-lyase activity is detected in the gel by incubating the gel with a reaction mixture containing alpha KMB (to ensure maintenance of the enzyme in the pyridoxal 5'-phosphate form), S-(1,2-dichlorovinyl)-L-cysteine (DCVC), PMS, and NBT. The products of the lyase reaction interact with PMS and NBT to form a blue dye coincident with the lyase activity. In addition, a new assay procedure for measuring cysteine S-conjugate beta-lyase activity was devised. This procedure couples pyruvate formation from DCVC to the alanine dehydrogenase reaction. Preparations of purified rat kidney glutamine transaminase K yield a single protein band on ND-PAGE (apparent Mr approximately 95,000). This band coincides with both the cysteine S-conjugate beta-lyase and glutamine transaminase K activities. Activity staining showed that homogenates of rat kidney, liver, skeletal muscle, and heart possess a glutamine transaminase K/cysteine S-conjugate beta-lyase activity with an Rf value on ND-PAGE identical to that of purified rat kidney glutamine transaminase K.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

High activities of glutamine transaminase K (dichlorovinylcysteine beta-lyase) and omega-amidase in the choroid plexus of rat brain.

Certain halogenated hydrocarbons, e.g., dichloroacetylene, are nephrotoxic to experimental animals and neurotoxic to humans; cysteine-S-conjugate beta-lyases may play a role in the nephrotoxicity. We now show that with dichlorovinylcysteine as substrate the only detectable cysteine-S-conjugate beta-lyase in rat brain homogenates is identical to glutamine transaminase K. The predominant (mitochondrial) form of glutamine transaminase K in rat brain was shown to be immunologically distinct from the predominant (cytosolic) form of the enzyme in rat kidney. Glutamine transaminase K and omega-amidase (constituents of the glutaminase II pathway) activities were shown to be widespread throughout the rat brain. However, the highest specific activities of these enzymes were found in the choroid plexus. The high activity of glutamine transaminase K in choroid plexus was also demonstrated by means of an immunohistochemical staining procedure. Glutamine transaminase K has a broad specificity toward amino acid and alpha-keto acid substrates. The omega-amidase also has a broad specificity; presumably, however, the natural substrates are alpha-ketoglutaramate and alpha-ketosuccinamate, the alpha-keto acid analogues of glutamine and asparagine, respectively. The high activities of both glutamine transaminase K and omega-amidase in the choroid plexus suggest that the two enzymes are linked metabolically and perhaps are coordinately expressed in that organ. The data suggest that the natural substrate of glutamine transaminase K in rat brain is indeed glutamine and that the metabolism of glutamine through the glutaminase II pathway (i.e., L-glutamine and alpha-keto acid-->alpha-ketoglutarate and L-amino acid + ammonia) is an important function of the choroid plexus. Moreover, the present findings also suggest that any explanation of the neurotoxicity of halogenated xenobiotics must take into account the role of glutamine transminase K and its presence in the choroid plexus.

Amidohydrolases↗
PubMed1974

Regulation of transaminase C synthesis in Escherichia coli: conditional leucine auxotrophy.

The regulation of synthesis of the valine-alanine-alpha-aminobutyrate transaminase (transaminase C) was studied in Escherichia coli mutants lacking the branched-chain amino acid transaminase (transaminase B). An investigation was made of two strains, CU2 and CU2002, each carrying the same transaminase B lesion but exhibiting different growth responses on a medium supplemented with branched-chain amino acids. Both had the absolute isoleucine requirement characteristic of ilvE auxotrophs, but growth of strain CU2 was stimulated by valine, whereas that of strain CU2002 was markedly inhibited by valine. Strain CU2002 behaved like a conditional leucine auxotroph in that the inhibition by valine was reversed by leucine. Results of enzymatic studies showed that synthesis of transaminase C was repressed by valine in strain CU2002 but not in strain CU2. Inhibition by valine in strain CU2002 appears to be the combined effect of repression on transaminase C synthesis and valine-dependent feedback inhibition of alpha-acetohydroxy acid synthase activity, causing alpha-ketoisovalerate (and hence leucine) limitation. The ilvE markers of strains CU2 and CU2002 were each transferred by transduction to a wild-type genetical background. All ilvE recombinants from both crosses resembled strain CU2002 and were inhibited by valine in the presence of isoleucine. Thus, strain CU2 carries an additional lesion that allows it to grow on a medium containing isoleucine plus valine. It is concluded that conditional leucine auxotrophy is characteristic of mutants carrying an ilvE lesion alone.

Culture Media↗
PubMed1979

Transaminase B from Escherichia coli: quaternary structure, amino-terminal sequence, substrate specificity, and absence of a separate valine-alpha-ketoglutarate activity.

Transaminase B (branched-chain amino acid aminotransferase, EC 2.6.1.42), the ilvE gene product, was purified to apparent homogeneity from an Escherichia coli K-12 strain which carries the ilvE gene both on the host chromosome and on a plasmid. The oligomeric structure of the enzyme, as determined by analytical ultracentrifugation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, was confirmed to be that of a hexamer with a molecular weight of about 182,000 and apparently identical subunits. Cross-linking with dimethylsuberimidate yielded trimers, dimers, and monomers, but essentially no species of higher molecular weight. These results are consistent with a double-trimer arrangement of the subunits in native enzyme. The amino-terminal sequence was found to be: Gly Thr Lys Lys Ala Asp Tyr Ile (Trp) Phe Asn Gly (Thr) (Met) Val. Purified transaminase B catalyzed transamination between alpha-ketoglutarate and l-isoleucine, l-leucine, l-valine, and, to a lesser extent, l-phenylalanine and l-tyrosine, the latter reacting very sluggishly. The enzyme was free of aspartate transaminase and of transaminase C. The apparent K(m) values for the branched-chain alpha-ketoacids were smaller than those for the corresponding amino acids. The lowest K(m) was recorded for dl-alpha-keto-beta-methyl-n-valerate, and the highest was recorded for l-valine. The ratio of the valine- and isoleucine-alpha-ketoglutarate activities did not change significantly during purification, and both activities were quantitatively removed from crude extract by antibody raised against purified transaminase B. These observations argue against the existence of a separate valine-alpha-ketoglutarate transaminase. Anti-E. coli transaminase B antibody cross-reacted with crude extract from Salmonella typhimurium, but not with extract obtained from Pseudomonas aeruginosa.

Amino Acid Sequence↗
PubMed1986

Segmental distribution and gestational changes of GABA-transaminase activity in the rat oviduct.

The occurrence and the localization of 4-aminobutyrate:2-oxoglutarate transaminase (GABA-transaminase) in the non-pregnant and pregnant rat oviduct were examined using biochemical and enzyme histochemical techniques. Specific GABA-transaminase activity was detected in the ampullary and isthmic portions of the oviduct as well as in the utero-tubal junction. The enzymic activity was lower in the ampullary than in the isthmic or intramural segments of the oviduct. Pregnancy induced a significant increase of GABA-transaminase activity in each portion of the oviduct. Enzyme histochemistry showed the highest GABA-transaminase reactivity at the level of the epithelial cells of the oviduct irrespective of the portion of the tube examined. A faint specific activity was demonstrated in the smooth muscle of the oviduct while the serosa did not show specific staining. Our findings indicate that: the observed increase of GABA-transaminase activity in the oviduct of the pregnant rat may be responsible for the reduced GABA levels in the oviduct during gestation; and the extraneuronal localization of GABA-transaminase activity does not seem to support the suggestion of a possible GABAergic innervation of the oviduct.

4-Aminobutyrate Transaminase↗