Reinvestigation of the Catalytic Mechanism of Formyl-CoA Transferase, a Class III CoA-transferase

Identification and characterization of two bile acid coenzyme A transferases from Clostridium scindens, a bile acid 7α-dehydroxylating intestinal bacterium

“…This mechanism suggests that a ternary complex is not formed as observed in family II transferases. Instead, the reaction is completed before reaction products are released ( 26 ). involved in bile acid CoA transfer by the baiF and possibly the baiK genes to that proposed for the FRC.…”

Succinyl-CoA:3-Sulfinopropionate CoA-Transferase from Variovorax paradoxus Strain TBEA6, a Novel Member of the Class III Coenzyme A (CoA)-Transferase Family

“…The mechanism proceeds via the formation of anhydrides between a highly conserved aspartate residue (Asp169 with respect to crotonobetainyl-CoA:carnitine CoAtransferase [CaiB] from E. coli) in the active site and the substrates. Crystal structure analysis and kinetic experiments indicate that the reaction is completed prior to the release of any product (20). Consequently, two different mechanisms were discovered, which close the active site during catalysis.…”

“…Their primary structures showed only few conserved amino acids, which makes it difficult to predict the structural conservation within this family (26). Nonetheless, the crystal structures of several representatives have been elucidated (20,(26)(27)(28)(29)(30). They indicate that family III CoAtransferases appear as intertwined dimers in which each monomer forms a ring with a hole in the center through which the other monomer is threaded (29).…”

“…Reverse transcription (RT)-PCR analyses of RNA from the wild type revealed constitutive transcription of this gene, irrespective of whether TDP or succinate was present as the sole source of carbon and energy (19). CoA-transferases catalyze the reversible transfer reaction of CoA from a donor to a free acid by formation of a CoA thioester (20,21). Therefore, it was expected that the translational product catalyzes the activation of 3SP to its corresponding CoA ester.…”

“…Consequently, two different mechanisms were discovered, which close the active site during catalysis. In the first mechanism, a glycine-rich loop takes different conformations as described for formyl CoA-transferase (20,(26)(27)(28)31). For CaiB from Escherichia coli, a representative of the second mechanism, the binding of the CoA triggers a domain shift that leads to the closure of the active site (30).…”