In some bacteria the enzyme catalyses the conversion of acetate to acetyl-CoA as part of a modified tricarboxylic acid (TCA) cycle [3,5,6]. In other organisms it converts acetyl-CoA to acetate during fermentation [1,2,4,7]. In some organisms the enzyme also catalyses the activity of EC 2.8.3.27, propanoyl-CoA:succinate CoA transferase.
the general half-reaction for class I CoA-transferases shows two tetrahedral oxyanion intermediates, which differ by whether CoA becomes attached to the external carbonyl, provided by the acyl-CoA/carboxylate substrate, or the internal carbonyl, provided by the essential active-site glutamate. Following exchange of the carboxylate product, the second half-reaction proceeds in the reverse order of the first half-reaction. In the first half-reaction, the binary enzyme·acyl-CoA complex is converted into a CoA thiolate complex that also contains an acylglutamyl anhydride adduct. Ping-pong kinetic mechanism. Val270 has a dual influence on carboxylate substrate selectivity, as a gate and as a clamp, Arg228 has an important kinetic role in carboxylate substrate binding. The auxiliary site nonselectively binds carboxylates at the threshold of the catalytic pocket, while selectivity is enforced by the conserved gating residue Val270 and the interior of the catalytic pocke
the general half-reaction for class I CoA-transferases shows two tetrahedral oxyanion intermediates, which differ by whether CoA becomes attached to the external carbonyl, provided by the acyl-CoA/carboxylate substrate, or the internal carbonyl, provided by the essential active-site glutamate. Following exchange of the carboxylate product, the second half-reaction proceeds in the reverse order of the first half-reaction. In the first half-reaction, the binary enzyme·acyl-CoA complex is converted into a CoA thiolate complex that also contains an acylglutamyl anhydride adduct. Ping-pong kinetic mechanism. Val270 has a dual influence on carboxylate substrate selectivity, as a gate and as a clamp, Arg228 has an important kinetic role in carboxylate substrate binding. The auxiliary site nonselectively binds carboxylates at the threshold of the catalytic pocket, while selectivity is enforced by the conserved gating residue Val270 and the interior of the catalytic pocke
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SYSTEMATIC NAME
IUBMB Comments
succinyl-CoA:acetate CoA-transferase
In some bacteria the enzyme catalyses the conversion of acetate to acetyl-CoA as part of a modified tricarboxylic acid (TCA) cycle [3,5,6]. In other organisms it converts acetyl-CoA to acetate during fermentation [1,2,4,7]. In some organisms the enzyme also catalyses the activity of EC 2.8.3.27, propanoyl-CoA:succinate CoA transferase.
steady-state kinetic analysis using a Michaelis-Menten model, a substrate inhibition model, or a competitive inhibition model, overview. Arg228 has an important kinetic role in carboxylate substrate binding
steady-state kinetic analysis using a Michaelis-Menten model, a substrate inhibition model, or a competitive inhibition model, overview. Arg228 has an important kinetic role in carboxylate substrate binding
the enzyme belongs to the class I-CoA-transferases, which, typified by mitochondrial succinyl-CoA:3-oxoacid CoA-transferase, form multiple covalent adducts involving an essential glutamate residue. Arg228 is found in only AarC and several closely allied SCACT group sequences, EC 6.2.1
the succinyl-CoA:acetate CoA-transferase/succinyl-CoA synthetase pathway is encoded by 30 species belonging to 5 different phyla, showing that a diverse range of bacteria encode this pathway. The SCACT/SCS pathway is important for acetate formation in many branches of the tree of life
the succinyl-CoA:acetate CoA-transferase/succinyl-CoA synthetase pathway is encoded by 30 species belonging to 5 different phyla, showing that a diverse range of bacteria encode this pathway. The SCACT/SCS pathway is important for acetate formation in many branches of the tree of life
the enzyme belongs to the class I-CoA-transferases, which, typified by mitochondrial succinyl-CoA:3-oxoacid CoA-transferase, form multiple covalent adducts involving an essential glutamate residue. Arg228 is found in only AarC and several closely allied SCACT group sequences, EC 6.2.1
the enzyme is involved in fermentation of glucose (succinyl-CoA:acetate CoA-transferase/succinyl-CoA synthetase pathway). The enzyme is responsible for forming both acetate and propionate
the enzyme is involved in fermentation of glucose (succinyl-CoA:acetate CoA-transferase/succinyl-CoA synthetase pathway). The enzyme is responsible for forming both acetate and propionate
enzyme AarC is succinyl-coenzyme A:acetate CoA-transferase, which replaces succinyl-CoA synthetase in a variant citric acid cycle. This bypass appears to reduce metabolic demand for free CoA, reliance upon nucleotide pools, and the likely effect of variable cytoplasmic pH upon citric acid cycle flux
low concentrations of succinate stimulate the anaerobic pyruvate metabolism of hydrogenosomes. A major function of succinate may be the intraorganellar shuttling of CoA from acetate to succinate as complied by acetate/succinate CoA-transferase
the enzyme is an acetic acid resistance factor AarC that is required for acetate resistance by vinegar factory strain Acetobacter aceti 1023. The enzyme acts in a variant citric acid cycle that overoxidizes acetic acid to CO2, which then diffuses into the acidic culture medium
low concentrations of succinate stimulate the anaerobic pyruvate metabolism of hydrogenosomes. A major function of succinate may be the intraorganellar shuttling of CoA from acetate to succinate as complied by acetate/succinate CoA-transferase
the enzyme is an acetic acid resistance factor AarC that is required for acetate resistance by vinegar factory strain Acetobacter aceti 1023. The enzyme acts in a variant citric acid cycle that overoxidizes acetic acid to CO2, which then diffuses into the acidic culture medium
the nucleophilic glutamate is held at a near-ideal angle for attack as the thioester oxygen is forced into an oxyanion hole composed of Gly388 NH and CoA N2''. CoA is nearly immobile along its entire length during all stages of the enzyme reaction. Spatial and sequence conservation of key residues indicates that this mechanism is general among class I CoA-transferases, structural model for the AarC mechanism, overview. An auxiliary carboxylate binding site, located just outside the AarC catalytic pocket, contributes to the efficient recognition and conversion of the physiological carboxylate substrates. Protein conformational dynamics, overview. Arg228 has an important kinetic role in carboxylate substrate binding. Regulation of carboxylate access to the active-site glutamate, overview
the nucleophilic glutamate is held at a near-ideal angle for attack as the thioester oxygen is forced into an oxyanion hole composed of Gly388 NH and CoA N2''. CoA is nearly immobile along its entire length during all stages of the enzyme reaction. Spatial and sequence conservation of key residues indicates that this mechanism is general among class I CoA-transferases, structural model for the AarC mechanism, overview. An auxiliary carboxylate binding site, located just outside the AarC catalytic pocket, contributes to the efficient recognition and conversion of the physiological carboxylate substrates. Protein conformational dynamics, overview. Arg228 has an important kinetic role in carboxylate substrate binding. Regulation of carboxylate access to the active-site glutamate, overview
the nucleophilic glutamate is held at a near-ideal angle for attack as the thioester oxygen is forced into an oxyanion hole composed of Gly388 NH and CoA N2''. CoA is nearly immobile along its entire length during all stages of the enzyme reaction. Spatial and sequence conservation of key residues indicates that this mechanism is general among class I CoA-transferases, structural model for the AarC mechanism, overview. An auxiliary carboxylate binding site, located just outside the AarC catalytic pocket, contributes to the efficient recognition and conversion of the physiological carboxylate substrates. Protein conformational dynamics, overview. Arg228 has an important kinetic role in carboxylate substrate binding. Regulation of carboxylate access to the active-site glutamate, overview
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CRYSTALLIZATION (Commentary)
ORGANISM
UNIPROT
LITERATURE
crystal structures of a C-terminally His6-tagged form of several wild-type and mutant complexes, including freeze-trapped acetylglutamyl anhydride and glutamyl-CoA thioester adducts. The latter shows the acetate product bound to an auxiliary site that is required for efficient carboxylate substrate recognition. Mutant E294A crystallizes in a closed complex containing dethiaacetyl-CoA, which adopts an unusual curled conformation. A model of the acetyl-CoA Michaelis complex reveals that the nucleophilic glutamate is held at a near-ideal angle for attack as the thioester oxygen is forced into an oxyanion hole composed of Gly388 NH and CoA N2'' CoA is nearly immobile along its entire length during all stages of the enzyme reaction
enzyme bound to dethiaacetyl-CoA and acetate, hanging drop vapor diffusion method, using 0.9 M sodium citrate, 0.1 M imidazole-HCl, pH 8.2, and 25 mM 2-mercaptoethanol
native and C-terminally His6-tagged wild-type enzymes in complexes including freeze-trapped acetylglutamyl anhydride and glutamyl-CoA thioester adducts, hanging drop vapor diffusion method, mixing of 0.002 ml of protein solution containing 5.6 mg/ml AarC in 45 mM potassium phosphate, pH 8.0, 90 mM potassium chloride, and 2 mM CoA or 6.0 mg/ml His6-tagged AarC in 45 mM Tris-HCl, pH 8.0, 90 mM potassium chloride, and 2 mM CoA, with 0.002 ml of reservoir solution containing 0.8-1.0 M sodium citrate, 0.1 M imidazole, pH 8.2, and 25 mM 2-mercaptoethanol for orthorhombic crystals or 1.7-2.0 M ammonium sulfate, 0.2 M sodium chloride, 0.1 M sodium cacodylate, pH 6.5, and 25 mM 2-mercaptoethanol for hexagonal crystals, room temperature of about 22°C, X-ray diffraction structure determination and analysis
site-directed mutagenesis, the mutant specific catalytic activity is 10000fold reduced compared to the wild-type enzyme, ligand bound crystal structure modeling
site-directed mutagenesis, the mutant is completely insoluble, ligand bound crystal structure determination and analysis, the mutant crystallizes in a closed complex containing dethiaacetyl-CoA, which adopts an unusual curled conformation
site-directed mutagenesis, the mutant catalytic properties are nearly equivalent to those of the His6-tagged wild-type enzyme, ligand bound crystal structure modeling
site-directed mutagenesis, the mutant shows impaired catalytic activity, but the apparent affinities for all four substrates are largely unaffected, ligand bound crystal structure modeling
site-directed mutagenesis, the mutant has a specific defect in its ability to bind both carboxylate substrates, ligand bound crystal structure modeling
A specialized citric acid cycle requiring succinyl-coenzyme A (CoA):acetate CoA-transferase (AarC) confers acetic acid resistance on the acidophile Acetobacter aceti
Crystal structures of Acetobacter aceti succinyl-coenzyme A (CoA):acetate CoA-transferase reveal specificity determinants and illustrate the mechanism used by class I CoA-transferases