Coenzyme A-transferase

Coenzyme A persulfide 790 Coenzyme A transferases 662 Coenzyme 788 Coenzyme M 813s, 814, 815 Coenzyme M reductase mechanism of 881 scheme 880... 

The pathway can be divided into two metabolic cycles (Figure 3.4). In the first cycle, acetyl-CoA is carboxylated to malonyl-CoA, which is subsequently reduced and converted into propionyl-CoA via 3-hydroxypropionate as a free intermediate. Propionyl-CoA is carboxylated to methylmalonyl-CoA, which is subsequently converted to succinyl-CoA the latter is then used to activate L-malate by succinyl-CoA L-malate coenzyme A transferase, which forms L-malyl-CoA and succinate. Succinate is oxidized to L-malate via conventional steps. L-Malyl-CoA, the second characteristic intermediate of this cycle, is cleaved by L-malyl-CoA/P-methylmalyl-CoA lyase, thus regenerating the starting molecule acetyl-CoA and releasing gly-oxylate as a first carbon-fixation product [27]. 

Resistance is conferred by the presence of an R factor, which codes for an acetyl coenzyme A transferase that inactivates chloramphenicol. Another mechanism for resistance is associated with an inability of the antibiotic to penetrate the organism. This change in permeability may be the basis of multidrug resistance. 

Coenzyme A must now be added to the acetoacetate. The thioester bond is a high energy bond, so ATP equivalents must be used. In this case the energy comes from a transesterification of the CoAS from succinyl CoA to acetoacetate by Coenzyme A transferase (2). The succinyl CoA comes from the TCA cycle where a GTP is not made. 

The phaG gene from Pseudomonas putida KT2440 encodes a 3-hydroxyacyl-acyl carrier protein-coenzyme A transferase. J. Biol. 

Buk) for butyrate. The proteins EtfA and EtfB are crucial for the activity of the Bed protein [56]. The required enzymes for solvent production are coenzyme A transferase (CtfA, CtfB), acetoacetate decarboxylase (Adc) as v rell as different aldehyde and alcohol dehydrogenases (BdhA, BdhB, AdhE, AdhE2). In C. beijer-inckii [57], an additional secondary alcohol dehydrogenase allows the reduction of acetone to isopropanol. All genes and enzymes were discussed in detail by Kopke andDiirre [58]. 

Wiesenborn, D.P., Rudolph, F.B, and Papoutsakis, E.T. (1989) Coenzyme A transferase from Clostridium acetobutylicum ATCC 824 and its role in the uptake of acids. Appl. Environ. Microbiol, 55, 323-329. 

Rehm BHA, Kruger N, Stembtichel A (1998) A new metabolic link between fatty acid de novo synthesis and polyhydroxyalkanoic acid synthesis the phaG gene from Pseudomonas putida KT2440 encodes a 3-hydroxyacyl-acyl carrier protein-coenzyme a transferase. J Biol Chem... 

Tummala SB, Junne SG, Papoutsakis ET. (2003a). Antisense RNA downregulation of coenzyme a transferase combined with alcohol-aldehyde dehydrogenase overexpression leads to predominantly alcohologenic Clostridium acetobutylicum fermentations. J Bacterial, 185, 3644-3653. 

Another way to generate particular acyl coenzyme A derivatives is at the expense of others. The succinyl-acetoacetyl coenzyme A transferase reaction is an important example. 

This is illustrated in Fig. 6 for the reaction of succinyl CoA acetoacetate coenzyme A transferase with its specific substrate succinyl CoA, compared with the corresponding nonenzymic reaction through the transition state [34]. Both reactions involve thiol interchange to form a new thiol ester of coenzyme A. Catalysis by the enzyme increases the reaction rate by a factor of 5 x 10, which corresponds to a stabilization of the transition state by 18.7 kcal moP Most of this stabilization arises from the utilization of noncovalent binding interactions between the coenzyme A moiety of the substrate and the enzyme. A short chain thiol ester of succinate with methyl mercaptopropionate has the same chemical properties as succinyl CoA but lacks the specific binding groups of the normal substrate this compound reacts with the enzyme some 10 more slowly than succinyl CoA, only an order of... 

Coenzyme A Transferases. In addition to enzymes that incorporate CoA into acyl thioesters, a group of enzymes have been found to form the CoA derivatives of certain acids by transfer of CoA from a preexisting thioester. The first example of this type of reaction to be found was the CoA transphorase of C. Muyveri. This enzyme transfers CoA among various small fatty acids. Bacterial enzymes have been implicated in CoA transfers between propionate and succinate, acetate and formate, ... 

Cary, J.W, Petersen, D.J., Papoutsakis, E.T., and Bennett, G.N. (1990) Cloning and expression of Clostridium acetobutylicum ATCC 824 acetoacetyl-coenzyme Aacetate/butyrate coenzyme A-transferase in Escherichia coli. Appl Envirorc Microbiol, 56, 1576—1583. 

Chotani G, Dodge T, Hsu A, Kumar M, LaDuca R, Trimbur D, Weyler W, Sanford K (2000) The commercial production of chemicals using pathway engineering. Biochim Biophys Acta 1543 434-455 Clark SW, Bennett GN, Rudolph FB (1989) Isolation and characterization of mutants of Clostridium acetobutylicum ATCC 824 deficient in acetoacetyl-coenzyme A acetate/butyrate coenzyme A-transferase (EC 2.8.3.9) and in other solvent pathway enzymes. Appl Environ Microbiol 55 970-976 Cocks GT, Aguilar J, Lin EGG (1974) Evolution of L-1,2-propanediol catabolism in Escherichia coli by recruitment of enzymes for L-fucose and L-lactate metabolism. J Bacteriol 118 83-88... 

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