This enzyme participates in fatty acid biosynthesis by providing one of the catalytic functions of the Acetyl-CoA carboxylase complex.

Malonyl-CoA serves as the primary carbon donor in fatty acid biosynthesis, followed by a series of reduction and dehydration reactions to remove the acyl group.

After this nucleophilic attack, the carbonate molecule is degraded to CO2 via electron pushing, producing a PO43- ion which then acts as a base and deprotonates the amide of the ureido ring within biotin.

The enolate then executes a nucleophilic attack on CO2 (which is being held in place through H-bonding with Glu296 residue), ultimately leading to the product of this enzymatic pathway: carboxybiotin.

While this change is thought to bring ATP within close enough proximity for the reaction to occur, the active site was still solvent exposed.

[4] The Glu296 and Arg338 are highly conserved residues among this subclass of enzymes, and work to stabilize the reaction intermediates and keep them within the active site pocket until the carboxylation is complete.