Citrate synthase

Definition

Citrate synthase is an essential enzyme in the citric acid cycle that catalyzes the condensation of acetyl-CoA and oxaloacetate to form citrate. This reaction is a critical step in cellular respiration, linking carbohydrate metabolism with energy production and the overall process of metabolism.

5 Must Know Facts For Your Next Test

1. Citrate synthase is located in the mitochondrial matrix, where it plays a pivotal role in the citric acid cycle.
2. The reaction catalyzed by citrate synthase is irreversible and regulated, ensuring that energy production is tightly controlled according to the cell's metabolic needs.
3. The activity of citrate synthase can be influenced by various factors including substrate availability, product inhibition by citrate, and allosteric regulation.
4. Deficiencies or mutations in the citrate synthase enzyme can lead to metabolic disorders and have been associated with certain diseases.
5. Citrate produced by citrate synthase can also serve as a precursor for fatty acid synthesis, linking energy metabolism with biosynthetic pathways.

Review Questions

• How does citrate synthase connect acetyl-CoA metabolism with energy production?
  • Citrate synthase connects acetyl-CoA metabolism with energy production by catalyzing the reaction between acetyl-CoA and oxaloacetate to form citrate. This reaction is crucial as it marks the entry of acetyl-CoA into the citric acid cycle, where it undergoes further oxidation to release energy stored in its chemical bonds. Without citrate synthase facilitating this first step, the entire cycle and subsequent ATP production would be impaired.
• Discuss how regulation of citrate synthase activity impacts cellular metabolism.
  • The regulation of citrate synthase activity is vital for maintaining metabolic homeostasis within cells. Since this enzyme catalyzes an irreversible step in the citric acid cycle, its activity is influenced by the availability of substrates like acetyl-CoA and oxaloacetate, as well as feedback inhibition from its product, citrate. When energy demand increases, higher levels of substrates stimulate citrate synthase activity, enhancing ATP production; conversely, when energy is abundant, product inhibition slows down the cycle to prevent overproduction of energy.
• Evaluate the implications of citrate synthase deficiencies on human health and metabolism.
  • Deficiencies in citrate synthase can have serious implications for human health and metabolism. Such deficiencies disrupt the normal functioning of the citric acid cycle, leading to reduced energy production which can result in fatigue and metabolic disorders. Additionally, because citrate is a key precursor for both energy generation and lipid synthesis, impaired enzyme function may cause dysregulation in fat metabolism and contribute to conditions such as obesity or diabetes. The broader impacts on cellular function emphasize how crucial this enzyme is for overall metabolic health.

Related terms

Acetyl-CoA:

A key molecule in metabolism that acts as a substrate for citrate synthase, derived from carbohydrates, fats, and proteins.

Citric Acid Cycle: A series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins.

Oxaloacetate:

A four-carbon molecule that combines with acetyl-CoA to form citrate in the first step of the citric acid cycle, playing a crucial role in energy metabolism.