Amino acid composition and terminal residues of aspartate aminotransferase from ox heart.
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ABSTRACT:
SUBMITTER: Marino G
PROVIDER: S-EPMC1265046 | biostudies-other | 1966 Jun
REPOSITORIES: biostudies-other
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Project description:1. A five-step procedure for preparing highly purified aspartate aminotransferase from ox heart is described. 2. The homogeneity of the pure enzyme was established by criteria such as ultracentrifugation and electrophoresis in starch gel and in polyacrylamide gel. 3. The pure enzyme has an isoelectric point of about pH5, and E(1%) (1cm.) 14.40 at 278mmu. 4. The molecular weight of the pure enzyme was determined as 96000 by sedimentation equilibrium. 5. The pH optimum for the pure enzyme was about 8. It was determined by a new assay technique. 6. A difference in the electrophoretic migration rate between the enzyme from ox heart and brain and the enzyme from pig heart and brain suggests a species specificity rather than an organ specificity. 7. A new effect of deionization on the visible-absorption spectrum of the enzyme was observed.
| S-EPMC1265045 | biostudies-other
Project description:1. R-phycoerythrin from Ceramium rubrum and C-phycocyanin from Nostoc muscorum have been obtained in purified form by fractional crystallization, followed by chromatography and gel-filtration. 2. The amino acid composition of both chromoproteins was determined; 85% of the total weight of both was recovered as amino acids. 3. Alanine was identified as the only C-terminal amino acid of R-phycoerythrin, each molecule of which contained about 12 terminal groups. 4. Serine was identified as the only C-terminal group of C-phycocyanin.
| S-EPMC1206423 | biostudies-other
Project description:Aspartate: 2-oxoglutarate aminotransferase from the anaerobic protozoon Trichomonas vaginalis was purified to homogeneity and characterized. It is a dimeric protein of overall Mr approx. 100000. Only a single isoenzyme was found in T. vaginalis. The overall molecular and catalytic properties have features in common with both the vertebrate cytoplasmic and mitochondrial isoenzymes. The purified aspartate aminotransferase from T. vaginalis showed very high rates of activity with aromatic amino acids as donors and 2-oxoglutarate as acceptor. This broad-spectrum activity was restricted to aromatic amino acids and aromatic 2-oxo acids, and no significant activity was seen with other common amino acids, other than with the substrates and products of the aspartate: 2-oxoglutarate aminotransferase reaction. Co-purification and co-inhibition, by the irreversible inhibitor gostatin, of the aromatic amino acid aminotransferase and aspartate aminotransferase activities, in conjunction with competitive substrate experiments, strongly suggest that a single enzyme is responsible for both activities. Such high rates of aromatic amino acid aminotransferase activity have not been reported before in eukaryotic aspartate aminotransferase.
| S-EPMC1152940 | biostudies-other
Project description:1. The cytosolic aspartate aminotransferase was purified from human liver. 2. The isoenzyme contains four cysteine residues, only one of which reacts with 5,5'-dithiobis-(2-nitrobenzoic acid) in the absence of denaturing agents. 3. The amino acid sequence of the isoenzyme is reported, as determined from peptides produced by digestion with trypsin and with CNBr, and from sub-digestion of some of these peptides with Staphylococcus aureus V8 proteinase. 4. The isoenzyme shares 48% identity of amino acid sequence with the mitochondrial form from human heart. 5. Comparisons of the amino acid sequences of all known mammalian cytosolic aspartate aminotransferases and of the same set of mitochondrial isoenzymes are reported. The results indicate that the cytosolic isoenzymes have evolved at about 1.3 times the rate of the mitochondrial forms. 6. The time elapsed since the cytosolic and mitochondrial isoenzymes diverged from a common ancestral protein is estimated to be 860 x 10(6) years. 7. Experimental details and confirmatory data for the results presented here are given in a supplementary paper that has been deposited as a Supplementary Publication SUP 50158 (25 pages) at the British Library Document Supply Centre, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1990) 265, 5.
| S-EPMC1131781 | biostudies-other
Project description:As a potential drug to treat neurological diseases, the mechanism-based inhibitor (S)-4-amino-4,5-dihydro-2-furancarboxylic acid (S-ADFA) has been found to inhibit the γ-aminobutyric acid aminotransferase (GABA-AT) reaction. To circumvent the difficulties in structural studies of a S-ADFA-enzyme complex using GABA-AT, l-aspartate aminotransferase (l-AspAT) from Escherichia coli was used as a model PLP-dependent enzyme. Crystal structures of the E. coli aspartate aminotransferase with S-ADFA bound to the active site were obtained via cocrystallization at pH 7.5 and 8. The complex structures suggest that S-ADFA inhibits the transamination reaction by forming adducts with the catalytic lysine 246 via a covalent bond while producing 1 equiv of pyridoxamine 5'-phosphate (PMP). Based on the structures, formation of the K246-S-ADFA adducts requires a specific initial binding configuration of S-ADFA in the l-AspAT active site, as well as deprotonation of the ε-amino group of lysine 246 after the formation of the quinonoid and/or ketimine intermediate in the overall inactivation reaction.
| S-EPMC3013228 | biostudies-literature
Project description:1. The capacity of various amino acids to convert the pyridoxal form of aspartate aminotransferase into the pyridoxamine form has been investigated. 2. Glutamate has the highest converting capacity; aspartate, alpha-aminopimelate, alpha-aminoadipate and other amino acids follow. 3. The converting capacity of the various amino acids assayed is connected with their structural features. 4. A possible role of amino acids as secondary substrates of aspartate aminotransferase is suggested.
| S-EPMC1206790 | biostudies-other
Project description:Treatment of the recombinant bovine factor B with trypsin yielded a fragment (amino acid residues 62-175) devoid of coupling activity. Removal of the N-terminal Trp2-Gly3-Trp4 peptide resulted in a significant loss of coupling activity in the FB(DeltaW)(2)(-W)(4) deletion mutant. Sucrose density gradient centrifugation demonstrated co-sedimentation of recombinant factor B with the ADP/ATP carrier, which is present in preparations of H(+)-translocating F(0)F(1)-ATPase, but not in preparations of complex V. The N-terminally truncated factor B mutant FB(DeltaW)(2)(-W)(4) did not co-sediment with the ADP/ATP carrier. Recombinant factor B co-sedimented with partially purified membrane sector F(0), extracted from F(1)-stripped bovine submitochondrial particles with n-dodecyl-beta-d-maltoside. Factor B inhibited the passive proton conductance catalyzed by F(0) reconstituted into asolectin liposomes. A factor B mutant, bearing a photoreactive unnatural amino acid pbenzoyl-l-phenylalanine (pBpa) substituted for Trp2, cross-linked with F(0) subunits e and g as well as the ADP/ATP carrier. These results suggest that the N-terminal domain and, in particular, the proximal N-terminal amino acids are important for the coupling activity and protein-protein interactions of bovine factor B.
| S-EPMC2867672 | biostudies-literature
Project description: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 that about 25% of residues are conserved between these distantly related forms. 5. Experimental details and confirmatory data for the results presented here are given in a Supplementary Publication (SUP 50164, 25 pages) that has been deposited at the British Library Document Supply Centre, Boston Spa. Wetherby, West Yorkshire LS23 7 BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1991) 273, 5.
| S-EPMC1151238 | biostudies-other
Project description:Frailty is a common comorbidity associated with adverse events in patients with heart failure, and early recognition is key to improving its management. We hypothesized that the AST to ALT ratio (AAR) could be a marker of frailty in patients with heart failure. Data from the FRAGILE-HF study were analyzed. A total of 1327 patients aged ≥ 65 years hospitalized with heart failure were categorized into three groups based on their AAR at discharge: low AAR (AAR < 1.16, n = 434); middle AAR (1.16 ≤ AAR < 1.70, n = 487); high AAR (AAR ≥ 1.70, n = 406). The primary endpoint was one-year mortality. The association between AAR and physical function was also assessed. High AAR was associated with lower short physical performance battery and shorter 6-min walk distance, and these associations were independent of age and sex. Logistic regression analysis revealed that high AAR was an independent marker of physical frailty after adjustment for age, sex and body mass index. During follow-up, all-cause death occurred in 161 patients. After adjusting for confounding factors, high AAR was associated with all-cause death (low AAR vs. high AAR, hazard ratio: 1.57, 95% confidence interval, 1.02-2.42; P = 0.040). In conclusion, AAR is a marker of frailty and prognostic for all-cause mortality in older patients with heart failure.
| S-EPMC8184951 | biostudies-literature
Project description:The C-terminal sequence of a protein is involved in processes such as efficiency of translation termination and protein degradation. However, the general relationship between features of this C-terminal sequence and levels of protein expression remains unknown. Here, we identified C-terminal amino acid biases that are ubiquitous across the bacterial taxonomy (1,582 genomes). We showed that the frequency is higher for positively charged amino acids (lysine, arginine), while hydrophobic amino acids and threonine are lower. We then studied the impact of C-terminal composition on protein levels in a library of Mycoplasma pneumoniae mutants, covering all possible combinations of the two last codons. We found that charged and polar residues, in particular lysine, led to higher expression, while hydrophobic and aromatic residues led to lower expression, with a difference in protein levels up to fourfold. We further showed that modulation of protein degradation rate could be one of the main mechanisms driving these differences. Our results demonstrate that the identity of the last amino acids has a strong influence on protein expression levels.
| S-EPMC7246954 | biostudies-literature