Understanding the Role of Acetyl-CoA Carboxylase in Fatty Acid Synthesis: A Step-by-Step Guide

The reaction catalyzed by acetyl-CoA carboxylase.

Acetyl-CoA carboxylase (ACC) is an enzyme that catalyzes the carboxylation of acetyl-CoA to produce malonyl-CoA

Acetyl-CoA carboxylase (ACC) is an enzyme that catalyzes the carboxylation of acetyl-CoA to produce malonyl-CoA. This is a crucial biochemical reaction in fatty acid synthesis. The reaction is a two-step process and requires the involvement of several cofactors and substrates.

Step 1: Biotin carboxylation
In the first step, ACC catalyzes the carboxylation of a biotin cofactor. Biotin is a vitamin that is covalently attached to a lysine residue on the ACC enzyme. It acts as a carrier for the carboxyl group in the reaction. The carboxylation of biotin occurs through the transfer of a carbon dioxide (CO2) molecule to a biotin nitrogen atom. This step is energy-dependent and requires ATP. The resulting carboxybiotin is then ready for transfer to the acetyl-CoA substrate.

Step 2: Transfer of carboxyl group to acetyl-CoA
In the second step, the carboxyl group carried by biotin is transferred to the acetyl-CoA substrate. The carboxyl group is transferred as a carboxyl-enzyme intermediate. The enzyme activates the acetyl-CoA substrate by attaching it to a sulfhydryl group in the enzyme. This activated acetyl-CoA reacts with the carboxyl-enzyme intermediate, leading to the transfer of the carboxyl group from biotin to acetyl-CoA. This results in the formation of malonyl-CoA.

Once malonyl-CoA is formed, it can be used as a building block in the synthesis of fatty acids. It acts as a precursor for the production of long-chain fatty acids, which are important for energy storage and membrane synthesis in cells.

Overall, the reaction catalyzed by acetyl-CoA carboxylase is an important step in fatty acid synthesis. It involves the carboxylation of acetyl-CoA using a biotin cofactor and the transfer of the carboxyl group to form malonyl-CoA. This process is tightly regulated in cells to ensure an appropriate balance between fatty acid synthesis and other metabolic pathways.

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