Final answer:
Biotin is the cofactor required for acetyl CoA carboxylase, with magnesium ions playing a significant role in the carboxylation process.
Step-by-step explanation:
The cofactor required for acetyl CoA carboxylase is biotin. This enzyme is important in fatty acid synthesis as it catalyzes the conversion of acetyl-CoA to malonyl-CoA, a crucial step in the process of fatty acid chain elongation. The activity of acetyl CoA carboxylase is regulated through allosteric interactions and covalent modifications, such as phosphorylation and dephosphorylation, which respond to the energy state of the cell and insulin signaling, respectively.
Magnesium ions (Mg2+) are also required as they help in reducing the overall negative charge during the carboxylation process, assisting in the nucleophilic attack of the biotin moiety on the activated bicarbonate. This facilitates the transfer of the carboxyl group from biotin to acetyl-CoA, producing malonyl-CoA.