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Aspartate Aminotransferase

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16841. Aspartate Aminotransferase in Alfalfa Root Nodules : II. Immunological Distinction between Two Forms of the Enzyme Full Text available with Trip Pro

Aspartate Aminotransferase in Alfalfa Root Nodules : II. Immunological Distinction between Two Forms of the Enzyme Aspartate aminotransferase (AAT), a key enzyme in the biosynthesis of aspartate and asparagine, occurs as two forms in alfalfa (Medicago sativa L.), AAT-1 and AAT-2. Both forms were purified to near homogeneity, and high titer polyclonal antibodies produced to the native proteins. Alfalfa AAT-1 was purified from root suspension culture cells, while AAT-2 was purified from effective

1990 Plant physiology

16842. The unfolding and refolding of cytoplasmic aspartate aminotransferase from pig heart. Full Text available with Trip Pro

The unfolding and refolding of cytoplasmic aspartate aminotransferase from pig heart. The unfolding of cytoplasmic aspartate aminotransferase from pig heart in solutions of guanidinium chloride (GdnHCl) was studied. Data from protein fluorescence, c.d. and thiol-group reactivity indicated that the enzyme was unfolded in 6 M-GdnHCl. Spectroscopic studies showed that this unfolding was accompanied by dissociation of the pyridoxal 5'-phosphate cofactor. On dilution of the GdnHCl, re-activation

1989 Biochemical Journal

16843. The unfolding and attempted refolding of mitochondrial aspartate aminotransferase from pig heart. Full Text available with Trip Pro

The unfolding and attempted refolding of mitochondrial aspartate aminotransferase from pig heart. The unfolding of the mitochondrial isoenzyme of aspartate aminotransferase from pig heart in solutions of guanidinium chloride (GdnHCl) has been studied. By a number of criteria (enzyme activity, protein fluorescence, c.d., thiol-group reactivity), the enzyme was judged to be almost completely unfolded in 2 M-GdnHCl. On dilution of the GdnHCl, no re-activation of the enzyme could be observed

1990 Biochemical Journal

16844. Purification and Characterization of Aspartate Aminotransferase Isoenzymes from Carrot Suspension Cultures Full Text available with Trip Pro

Purification and Characterization of Aspartate Aminotransferase Isoenzymes from Carrot Suspension Cultures Three aspartate aminotransferase isoenzymes were identified from extracts of carrot (Daucus carota L.) cell suspension cultures. These isoenzymes were separated by DEAE chromatography and were analyzed on native gradient polyacrylamide gels. The relative molecular weights of the isoenzymes were 111,000 +/- 5000, 105,000 +/- 5000, and 94,000 +/- 4000 daltons; they were designated forms I (...) with AAT activity on the IEF-PAGE gel are a combination of hetero- and homodimers. Form I has a broad pH optimum of 7.5 to 10.0. K(m) values of 23.6, 2.8, 0.05, and 0.22 millimolar were obtained for glutamate, aspartate, oxaloacetate, and alpha-ketoglutarate, respectively. The mode of action is a ping-pong-bi-bi mechanism.

1990 Plant physiology

16845. Rapid Purification and Thermostability of the Cytoplasmic Aspartate Aminotransferase from Carrot Suspension Cultures Full Text available with Trip Pro

Rapid Purification and Thermostability of the Cytoplasmic Aspartate Aminotransferase from Carrot Suspension Cultures Several isoenzymic forms of aspartate aminotransferase (AAT) have been identified in protein extracts from carrot (Daucus carota) cell suspension cultures. The cellular location of the major form (form I) of AAT in carrot suspension cultures was determined by heat inactivation, subcellular fractionation, and amino acid sequence analysis. In mammalian systems, there are two forms

1991 Plant physiology

16846. Brønsted analysis of aspartate aminotransferase via exogenous catalysis of reactions of an inactive mutant. Full Text available with Trip Pro

Brønsted analysis of aspartate aminotransferase via exogenous catalysis of reactions of an inactive mutant. Primary amines functionally replace lysine 258 by catalyzing both the 1,3-prototropic shift and external aldimine hydrolysis reactions with the inactive aspartate aminotransferase mutant K258A. This finding allows classical Brønsted analyses of proton transfer reactions to be applied to enzyme-catalyzed reactions. An earlier study of the reaction of K258A with cysteine sulfinate (Toney (...) , M.D. & Kirsch, J.F., 1989, Science 243, 1485) provided a beta value of 0.4 for the 1,3-prototropic shift. The beta value reported here for the transamination of oxalacetate to aspartate is 0.6. The catalytic efficacy of primary amines is largely determined by basicity and molecular volume. The dependence of the rate constants for the reactions of K258A and K258M on amine molecular volume is nearly identical. This observation argues that the alkyl groups of the added amines do not occupy

1992 Protein science : a publication of the Protein Society

16847. Purification and characterization of aspartate aminotransferase from the halophile archaebacterium Haloferax mediterranei. Full Text available with Trip Pro

Purification and characterization of aspartate aminotransferase from the halophile archaebacterium Haloferax mediterranei. Aspartate aminotransferase from the archaebacterium Haloferax mediterranei was purified and found to be homogeneous. An average Mr of 66,000 was estimated. The native halophilic transaminase exhibited no maximum absorption at 410 nm, which indicates that the apo form is obtained by our purification procedure, and the molar absorption coefficient at 275 nm in 3.5 M-KCl (pH (...) 7.8) was found to be 78.34 mM-1.cm-1. Plots of titration data show that 1 mol of halophilic aspartate aminotransferase binds 2 mol of pyridoxal 5'-phosphate. The halophilic transaminase behaved as a dimer with two similar subunits and had a maximum activity in the pH range 7.6-7.9 and at 65 degrees C in 3.5 M-KCl. By differential scanning calorimetry, the denaturation temperature of the halophilic holo- and apo-transaminase was determined to be 78.5 and 68.0 degrees C respectively at 3.3 M-KCl (pH

1991 Biochemical Journal

16848. The amino acid sequence of the aspartate aminotransferase from baker's yeast (Saccharomyces cerevisiae). Full Text available with Trip Pro

The amino acid sequence of the aspartate aminotransferase from baker's yeast (Saccharomyces cerevisiae). 1. The single (cytosolic) aspartate aminotransferase was purified in high yield from baker's yeast (Saccharomyces cerevisiae). 2. Amino-acid-sequence analysis was carried out by digestion of the protein with trypsin and with CNBr; some of the peptides produced were further subdigested with Staphylococcus aureus V8 proteinase or with pepsin. Peptides were sequenced by the dansyl-Edman method (...) and/or by automated gas-phase methods. The amino acid sequence obtained was complete except for a probable gap of two residues as indicated by comparison with the structures of counterpart proteins in other species. 3. The N-terminus of the enzyme is blocked. Fast-atom-bombardment m.s. was used to identify the blocking group as an acetyl one. 4. Alignment of the sequence of the enzyme with those of vertebrate cytosolic and mitochondrial aspartate aminotransferases and with the enzyme from Escherichia coli showed

1991 Biochemical Journal

16849. Chromosomal deletions around the albino locus in the mouse cause loss of hormone-inducible expression of the unlinked structural gene encoding cytosolic aspartate aminotransferase. Full Text available with Trip Pro

Chromosomal deletions around the albino locus in the mouse cause loss of hormone-inducible expression of the unlinked structural gene encoding cytosolic aspartate aminotransferase. A group of genes in the mouse encoding liver-specific gluconeogenic enzymes and mapping on different chromosomes lose their normal competence for hormone-inducible expression in animals homozygous for chromosomal deletions around the albino locus on chromosome 7. The basal expression of these same genes remains (...) normal. In previous investigations, glucocorticoid hormones as well as their receptors were found to be normal in the deletion homozygotes. The results reported here identify an additional unlinked structural gene whose regulation appears to be affected by the deletions--i.e., that encoding cytosolic aspartate aminotransferase, a housekeeping gene that participates in gluconeogenesis in the liver. In normal mice, its mRNA level increases sharply at birth, specifically in the liver, and can

1995 Proceedings of the National Academy of Sciences of the United States of America

16850. Phorbol esters inhibit the glucocorticoid-mediated stimulation of cytosolic aspartate aminotransferase gene transcription. Full Text available with Trip Pro

Phorbol esters inhibit the glucocorticoid-mediated stimulation of cytosolic aspartate aminotransferase gene transcription. The regulation of cytosolic aspartate aminotransferase (cAspAT) gene expression by phorbol esters was investigated in the highly differentiated hepatoma cell line Fao. Phorbol 12,13-dibutyrate (PdBu) had no effect on basal activity but partially inhibited the induction of cAspAT by dexamethasone. The extent of inhibition (40%) was similar to that obtained with insulin

1994 Biochemical Journal

16851. The use of natural and unnatural amino acid substrates to define the substrate specificity differences of Escherichia coli aspartate and tyrosine aminotransferases. Full Text available with Trip Pro

The use of natural and unnatural amino acid substrates to define the substrate specificity differences of Escherichia coli aspartate and tyrosine aminotransferases. The tyrosine (eTATase) and aspartate (eAATase) aminotransferases of Escherichia coli transaminate diacarboxylic amino acids with similar rate constants. However, eTATase exhibits approximately 10(2)-10(4)-fold higher second-order rate constants for the transamination of aromatic amino acids than does eAATase. A series of natural (...) and unnatural amino acid substrates was used to quantitate specificity differences for these two highly related enzymes. A general trend toward lower transamination activity with increasing side-chain length (extending from aspartate to glutamate to alpha-aminoadipate) is observed for both enzymes. This result suggests that dicarboxylate ligands associate with the two highly related enzymes in a similar manner. The high reactivity of the enzymes with L-Asp and L-Glu can be attributed to an ion pair

1995 Protein science : a publication of the Protein Society

16852. Identification and Expression of a cDNA Clone Encoding Aspartate Aminotransferase in Carrot Full Text available with Trip Pro

Identification and Expression of a cDNA Clone Encoding Aspartate Aminotransferase in Carrot A full-length cDNA clone encoding aspartate aminotransferase (AAT) has been identified from a carrot root cDNA library. Degenerate oligo primers were synthesized from the known amino acid sequence of AAT form I from carrot (Daucus carota L. cv Danvers). These primers were utilized in a polymerase chain reaction to amplify a portion of a carrot AAT gene from first strand cDNA synthesized from poly

1992 Plant physiology

16853. Cloning and characterization of a cDNA encoding aspartate aminotransferase-P1 from Lupinus angustifolius root tips. Full Text available with Trip Pro

Cloning and characterization of a cDNA encoding aspartate aminotransferase-P1 from Lupinus angustifolius root tips. A root tip cDNA library, constructed in the lambda Zap II expression vector, was immunoscreened with a monoclonal antibody raised against aspartate aminotransferase-P1 from Lupinus angustifolius L. var Uniharvest. One 1452-base pair clone was isolated. The encoded protein sequence had high homology to both plant and animal aspartate aminotransferase sequences. The clone (...) was converted to the phagemid form and expressed in Escherichia coli. The expressed protein was enzymically active and could be immunocomplexed with aspartate aminotransferase-P1-specific antibodies. The complete aspartate aminotransferase-P1 cDNA was cloned into the yeast expression vector pEMBL-yex4 and transformed into Saccharomyces cerevisiae strain BRSCS6, which possesses a mutated aspartate aminotransferase gene (the asp5 mutation). Complementation of the mutation was achieved using this construct.

1994 Plant physiology

16854. Further thermal characterization of an aspartate aminotransferase from a halophilic organism. Full Text available with Trip Pro

Further thermal characterization of an aspartate aminotransferase from a halophilic organism. Aspartate aminotransferase (AspAT, EC 2.6.1.1) from the halophilic archaebacterium Haloferax mediterranei was purified [Muriana, Alvarez-Ossorio and Relimpio (1991) Biochem. J. 278, 149-154] and further characterization of the effects of temperature on the activity and stability of the halophilic AspAT were carried out. The halophilic transaminase is most active at 65 degrees C and stable at high

1994 Biochemical Journal

16855. The aspartate aminotransferase-P1 gene from Lupinus angustifolius. Full Text available with Trip Pro

The aspartate aminotransferase-P1 gene from Lupinus angustifolius. 8066141 1994 09 20 2018 11 13 0032-0889 105 2 1994 Jun Plant physiology Plant Physiol. The aspartate aminotransferase-P1 gene from Lupinus angustifolius. 763-4 Kirk C A CA Plant Improvement Division, Horticulture and Food Research Institute of New Zealand, Palmerston North. Mett V V Reynolds P H PH eng GENBANK L23875 Journal Article United States Plant Physiol 0401224 0032-0889 0 DNA, Complementary 0 Isoenzymes EC 2.6.1.1 (...) Aspartate Aminotransferases IM AAT-P1 Aspartate Aminotransferases genetics Base Sequence Cloning, Molecular DNA, Complementary genetics Fabaceae enzymology genetics Gene Expression Genes, Plant Isoenzymes genetics Molecular Sequence Data Plants, Medicinal 1994 6 1 1994 6 1 0 1 1994 6 1 0 0 ppublish 8066141 PMC159424 Eur J Biochem. 1990 Aug 28;192(1):119-26 2401287 Plant Physiol. 1992 Mar;98(3):868-78 16668758 Plant Physiol. 1994 Feb;104(2):417-23 8159784 Plant Mol Biol. 1992 Jun;19(3):465

1994 Plant physiology

16856. Thermal inactivation and chaperonin-mediated renaturation of mitochondrial aspartate aminotransferase. Full Text available with Trip Pro

Thermal inactivation and chaperonin-mediated renaturation of mitochondrial aspartate aminotransferase. Mitochondrial aspartate aminotransferase is inactivated irreversibly on heating. The inactivated protein aggregates, but aggregation is prevented by the presence of the chaperonin 60 from Escherichia coli (GroEL). The chaperonin increases the rate of thermal inactivation in the temperature range 55-65 degrees C but not at lower temperatures. It has previously been shown [Twomey and Doonan

1998 Biochemical Journal

16857. The role of the conserved Lys68*:Glu265 intersubunit salt bridge in aspartate aminotransferase kinetics: Multiple forced covariant amino acid substitutions in natural variants Full Text available with Trip Pro

The role of the conserved Lys68*:Glu265 intersubunit salt bridge in aspartate aminotransferase kinetics: Multiple forced covariant amino acid substitutions in natural variants The role of the Lys68*:Glu265 intersubunit salt bridge that is conserved (Csb) in all known aspartate aminotransferases (AATases), except those of animal cytosolic, Ac (His68*:Glu265), and plant mitochondrial, Pm (Met68*:Gln265), origins, was evaluated in the Escherichia coli AATase. Two double-mutant cycles, to K68M

2002 Protein science : a publication of the Protein Society

16858. Re-activation by glutamate or aspartate of amino-oxyacetate-inhibited aspartate aminotransferase in vitro and in isolated hepatocytes Full Text available with Trip Pro

Re-activation by glutamate or aspartate of amino-oxyacetate-inhibited aspartate aminotransferase in vitro and in isolated hepatocytes Experiments with isolated rat hepatocytes and with cell extracts indicate, in contrast with previous reports, that pyruvate does not block or reverse the inhibition of aspartate aminotransferase (EC 2.6.1.1) by amino-oxyacetate. That inhibition, however, is partially overcome by glutamate or aspartate either in cell extracts or in whole cells incubated

1981 Biochemical Journal

16859. Aspartate aminotransferase activity is required for aspartate catabolism and symbiotic nitrogen fixation in Rhizobium meliloti. Full Text available with Trip Pro

Aspartate aminotransferase activity is required for aspartate catabolism and symbiotic nitrogen fixation in Rhizobium meliloti. A mutant of Rhizobium meliloti, 4R3, which is unable to grow on aspartate has been isolated. The defect is specific to aspartate utilization, since 4R3 is not an auxotroph and grows as well as its parent strain on other carbon and nitrogen sources. The defect was correlated with an inability to fix nitrogen within nodules formed on alfalfa. Transport of aspartate (...) into the mutant cells was found to be normal. Analysis of enzymes involved in aspartate catabolism showed a significantly lower level of aspartate aminotransferase activity in cell extracts of 4R3 than in the wild type. Two unrelated regions identified from a genomic cosmid bank each complemented the aspartate catabolism and symbiotic defects in 4R3. One of the cosmids was found to encode an aspartate aminotransferase enzyme and resulted in restoration of aspartate aminotransferase activity in the mutant

1991 Journal of bacteriology

16860. Kynurenine aminotransferase and glutamine transaminase K of Escherichia coli: identity with aspartate aminotransferase. Full Text available with Trip Pro

Kynurenine aminotransferase and glutamine transaminase K of Escherichia coli: identity with aspartate aminotransferase. The present study describes the isolation of a protein from Escherichia coli possessing kynurenine aminotransferase (KAT) activity and its identification as aspartate aminotransferase (AspAT). KAT catalyses the transamination of kynurenine and 3-hydroxykynurenine to kynurenic acid and xanthurenic acid respectively, and the enzyme activity can be easily detected in E. coli

2001 Biochemical Journal

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