| Type: | Family | Name: | L-carnitine CoA-transferase CaiB |
| Description: | CoA-transferases are found in organisms from all kingdoms of life. They catalyse reversible transfer reactions of coenzyme A groups from CoA-thioesters to free acids. There are at least three families of CoA-transferases, which differ in sequence and reaction mechanism:Family I consists of CoA-transferases for 3-oxoacids (, ), short-chain fatty acids (, ) and glutaconate (). Most use succinyl-CoA or acetyl-CoA as CoA donors.Family II consists of the homodimeric alpha-subunits of citrate lyase and citramalate lyase (, ). These enzymes catalyse the transfer of acyl carrier protein (ACP) with a covalently bound CoA derivative, but can accept free CoA thioesters as well.Family III consists of formyl-CoA:oxalate CoA-transferase [], succinyl-CoA:(R)-benzylsuccinate CoA-transferase [], (E)-cinnamoyl-CoA:(R)-phenyllactate CoA-transferase [], and butyrobetainyl-CoA:(R)-carnitine CoA-transferase []. These CoA-transferases occur in prokaryotes and eukaryotes, and catalyse CoA-transfer reactions in a highly substrate- and stereo-specific manner [].CaiB is a family III CoA-transferase that catalyzes the reversible transfer of the CoA moiety from gamma-butyrobetainyl-CoA to L-carnitine to generate L-carnitinyl-CoA and gamma-butyrobetaine []. This enzyme can also catalyse the reversible transfer of the CoA moiety from gamma-butyrobetainyl-CoA or L-carnitinyl-CoA to crotonobetaine to generate crotonobetainyl-CoA.In Escherichia coli, CaiB is one of the genes encoded by the caiTABCDE operon []. The adjacent but divergent fixABCD operon also appears to be necessary for carnintine meatbolism []. CaiB is composed of two identical circular chains that together form an intertwined dimer. Each monomer consists of a large domain, containing a Rossmann fold, and a small domain []. | Short Name: | CoA-Trfase_CaiB |
