key term - Carnitine palmitoyltransferase I

Definition

Carnitine palmitoyltransferase I (CPT I) is an enzyme located on the outer mitochondrial membrane that plays a critical role in the transport of long-chain fatty acids into mitochondria for beta-oxidation. This enzyme catalyzes the conversion of acyl-CoA to acylcarnitine, allowing fatty acids to cross the mitochondrial membrane. The activity of CPT I is essential for efficient fatty acid degradation and is closely linked to lipid metabolism and energy production in the body.

5 Must Know Facts For Your Next Test

1. CPT I is inhibited by malonyl-CoA, a key metabolite that signals when energy stores are sufficient, preventing the breakdown of fatty acids during active lipogenesis.
2. The conversion process catalyzed by CPT I is crucial because long-chain fatty acids cannot directly enter mitochondria without being converted to acylcarnitines.
3. There are different isoforms of CPT I, with CPT I-A and CPT I-B located in various tissues, indicating specialized functions in fatty acid metabolism.
4. Deficiency in CPT I can lead to impaired fat metabolism, resulting in conditions such as hypoketotic hypoglycemia and muscle weakness during fasting.
5. CPT I activity is influenced by nutritional status, hormonal regulation, and the availability of substrates, making it an important point of regulation in energy homeostasis.

Review Questions

• How does carnitine palmitoyltransferase I facilitate the transport of fatty acids into mitochondria?
  • Carnitine palmitoyltransferase I facilitates the transport of fatty acids by converting acyl-CoA into acylcarnitine, which can then cross the outer mitochondrial membrane. Once inside the mitochondria, acylcarnitine is converted back into acyl-CoA by carnitine palmitoyltransferase II. This process is essential for initiating beta-oxidation, where fatty acids are broken down to produce energy.
• Discuss the regulatory mechanisms that influence the activity of carnitine palmitoyltransferase I.
  • The activity of carnitine palmitoyltransferase I is primarily regulated by malonyl-CoA, which inhibits the enzyme when energy reserves are sufficient. This inhibition prevents fatty acid breakdown during periods of active lipid synthesis. Additionally, hormones such as insulin and glucagon also play a role in regulating CPT I activity based on metabolic state, ensuring that the body efficiently manages its energy resources.
• Evaluate the impact of carnitine palmitoyltransferase I deficiency on metabolic processes and overall health.
  • Deficiency in carnitine palmitoyltransferase I can lead to serious metabolic disruptions, particularly in fat metabolism. Individuals with this deficiency may experience symptoms such as hypoketotic hypoglycemia during fasting periods due to impaired fatty acid oxidation. This condition can result in muscle weakness and an inability to effectively utilize stored fat for energy during times of increased demand. Overall health can be significantly compromised if dietary management and supplementation are not implemented to support energy needs.

Related terms

Beta-oxidation: The metabolic process by which fatty acids are broken down in the mitochondria to generate acetyl-CoA, NADH, and FADH2.

Carnitine: A quaternary ammonium compound derived from amino acids that facilitates the transport of fatty acids into the mitochondria.

Fatty acid synthase: A multi-enzyme complex responsible for synthesizing fatty acids from acetyl-CoA and malonyl-CoA during fatty acid synthesis.