Acetyl-CoA Carboxylase

Definition

Acetyl-CoA carboxylase is an essential enzyme that catalyzes the conversion of acetyl-CoA into malonyl-CoA, a crucial step in fatty acid biosynthesis. This enzyme plays a key role in lipid metabolism, as malonyl-CoA serves as the building block for fatty acid chains. The regulation of acetyl-CoA carboxylase is vital for maintaining the balance between lipid synthesis and degradation, influencing energy storage and membrane formation.

5 Must Know Facts For Your Next Test

1. Acetyl-CoA carboxylase is activated by citrate, which indicates an abundance of substrates for fatty acid synthesis.
2. The enzyme exists in two isoforms: ACC1, primarily found in the cytoplasm, and ACC2, located in mitochondria, highlighting different regulatory roles in lipid metabolism.
3. Phosphorylation of acetyl-CoA carboxylase by AMPK leads to its inhibition, thus reducing fatty acid synthesis during energy deprivation.
4. Malonyl-CoA not only contributes to fatty acid synthesis but also inhibits fatty acid oxidation by preventing the transport of fatty acids into mitochondria.
5. Dysregulation of acetyl-CoA carboxylase activity can lead to metabolic disorders such as obesity and insulin resistance.

Review Questions

• How does acetyl-CoA carboxylase contribute to fatty acid biosynthesis, and what role does malonyl-CoA play in this process?
  • Acetyl-CoA carboxylase catalyzes the conversion of acetyl-CoA to malonyl-CoA, which is critical for fatty acid biosynthesis. Malonyl-CoA serves as the primary building block for the elongation of fatty acid chains within the fatty acid synthase complex. This process allows cells to synthesize long-chain fatty acids necessary for energy storage and membrane formation.
• Discuss the regulatory mechanisms that control acetyl-CoA carboxylase activity and their significance in cellular metabolism.
  • Acetyl-CoA carboxylase activity is primarily regulated through allosteric effects and covalent modification. Citrate acts as an allosteric activator, signaling sufficient substrates for lipid synthesis, while phosphorylation by AMPK inhibits its activity during low energy states. These regulatory mechanisms ensure that fatty acid synthesis is tightly coordinated with the cell's energy needs and overall metabolic state.
• Evaluate the implications of altered acetyl-CoA carboxylase activity on metabolic health and disease states such as obesity.
  • Altered activity of acetyl-CoA carboxylase can significantly impact metabolic health, leading to conditions such as obesity and insulin resistance. When acetyl-CoA carboxylase is overactive, it can lead to excessive fatty acid synthesis and accumulation of lipids, contributing to metabolic syndrome. Conversely, reduced activity may impair lipid biosynthesis and affect energy storage, demonstrating the importance of proper regulation of this enzyme in maintaining metabolic balance.

Related terms

Fatty Acid Synthase: A multi-enzyme complex responsible for the synthesis of fatty acids from acetyl-CoA and malonyl-CoA.

Malonyl-CoA: The product of acetyl-CoA carboxylase's reaction, which acts as a key substrate in the elongation of fatty acid chains.

AMP-activated Protein Kinase (AMPK): An energy-sensing enzyme that regulates metabolic pathways, including the inhibition of acetyl-CoA carboxylase when cellular energy levels are low.