key term - Fatty acid synthase complex

Definition

The fatty acid synthase complex is a multi-enzyme protein complex responsible for the synthesis of fatty acids from acetyl-CoA and malonyl-CoA, using NADPH as a reducing agent. This complex plays a crucial role in lipid metabolism and is vital for producing long-chain fatty acids that are essential for various cellular functions, including energy storage and membrane formation.

5 Must Know Facts For Your Next Test

1. The fatty acid synthase complex operates in the cytoplasm of eukaryotic cells, allowing efficient access to substrates like acetyl-CoA and NADPH.
2. This complex is a dimeric enzyme, meaning it consists of two identical polypeptide chains that work together during the fatty acid synthesis process.
3. Fatty acid synthesis primarily occurs when carbohydrate intake is high, as excess carbohydrates can be converted into acetyl-CoA for fatty acid production.
4. The end product of the fatty acid synthase complex is typically palmitate, which can be further elongated or desaturated to form other types of fatty acids.
5. Regulation of the fatty acid synthase complex is closely linked to hormonal control, particularly insulin, which promotes lipid biosynthesis when energy stores are plentiful.

Review Questions

• How does the structure of the fatty acid synthase complex contribute to its function in fatty acid synthesis?
  • The fatty acid synthase complex's dimeric structure allows for efficient coordination of multiple enzymatic activities involved in fatty acid synthesis. This arrangement facilitates the sequential addition of two-carbon units derived from malonyl-CoA to a growing fatty acyl chain. The proximity of active sites within the complex also enhances substrate channeling, reducing potential loss of intermediates and increasing overall reaction efficiency.
• Discuss the impact of substrate availability on the activity of the fatty acid synthase complex.
  • The activity of the fatty acid synthase complex is heavily influenced by the availability of its substrates: acetyl-CoA and NADPH. When carbohydrate levels are high, more acetyl-CoA is produced through glycolysis, leading to increased fatty acid synthesis. Similarly, higher levels of NADPH generated by the pentose phosphate pathway provide the necessary reducing power for the enzymatic reactions in the complex. Therefore, fluctuations in nutrient availability directly impact lipid biosynthesis and energy storage.
• Evaluate how hormonal regulation affects the function of the fatty acid synthase complex and its implications for metabolic health.
  • Hormonal regulation plays a crucial role in controlling the activity of the fatty acid synthase complex. Insulin promotes lipogenesis by enhancing the expression and activity of this complex when energy stores are sufficient. Conversely, glucagon inhibits its activity during fasting states to prevent excess fat storage. Dysregulation of this balance can lead to metabolic disorders such as obesity and type 2 diabetes, highlighting the importance of proper hormonal signaling in maintaining metabolic health.

Related terms

Acetyl-CoA: A two-carbon molecule that serves as a key building block in the synthesis of fatty acids and is also a critical intermediate in several metabolic pathways.

NADPH:

Nicotinamide adenine dinucleotide phosphate, a reducing agent used in anabolic reactions, including the fatty acid synthesis process.

Palmitate: A common saturated fatty acid produced by the fatty acid synthase complex, consisting of 16 carbon atoms.