In molecular biology, proteins containing the carboxyl transferase domain include biotin-dependent carboxylases.

[1][2] This domain carries out the following reaction: transcarboxylation from biotin to an acceptor molecule.

There are two recognised types of carboxyl transferase.

One of them uses acyl-CoA and the other uses 2-oxo acid as the acceptor molecule of carbon dioxide.

All of the members in this family use acyl-CoA as the acceptor molecule.