PROSITE documentation PDOC00980

Coenzyme A transferases signatures

Coenzyme A (CoA) transferases are enzymes catalyzing the reversible transfer of CoA from one carboxylic acid to another. They have been identified in many prokaryotes and in mammalian tissues. They belong to an evolutionary conserved [1,2] family of proteins that consist of:

• Succinyl CoA:3-oxoacid CoA transferase (EC 2.8.3.5) (SCOT), which is responsible for the formation of acetoacetyl CoA by transfer of a CoA moiety from succinyl-CoA to a 3-oxoacid, usually acetoacetate. In higher eukaryotes it is a mitochondrial enzyme which plays a crucial role in ketone body metabolism. It has also been found in bacteria.
• Bacterial 3-oxoadipate CoA-transferase (EC 2.8.3.6) which carries out the penultimate step in the conversion of benzoate and 4-hydroxybenzoate to tricarboxylic acid cycle intermediates in bacteria utilizing the β- ketoadipate pathway.
• Bacterial acetate CoA-transferase (EC 2.8.3.8).
• Clostridial butyrate-acetoacetate CoA-transferase (EC 2.8.3.9), which acts mainly to detoxify the medium by removing the acetate and butyrate excreted earlier in the fermentation.

The bacterial enzymes are heterodimer of two subunits (A and B) of about 25 Kd each while eukaryotic SCOT consist of a single chain which is colinear with the two bacterial subunits.

We developed two signature patterns for these enzymes. The first corresponds to a region in the N-terminal of the A subunit that may be implicated in the binding of CoA to the enzyme. The second corresponds to a region in the N-terminal of the B subunit and contains a glutamate that is involved in the catalytic mechanism [3].