Citrate synthase

Definition

Citrate synthase is an essential enzyme in the citric acid cycle (Krebs cycle) that catalyzes the condensation of acetyl-CoA and oxaloacetate to form citrate. This reaction is a critical step in carbohydrate metabolism, linking the breakdown of carbohydrates to the energy-producing processes of cellular respiration.

5 Must Know Facts For Your Next Test

1. Citrate synthase is regulated by the availability of its substrates, primarily acetyl-CoA and oxaloacetate, making it a crucial control point in the citric acid cycle.
2. The enzyme operates through a two-step mechanism: first, it binds to oxaloacetate to form a transient intermediate before reacting with acetyl-CoA to produce citrate.
3. Citrate synthase is found in the mitochondria of eukaryotic cells and plays a key role in linking glycolysis (carbohydrate metabolism) to aerobic respiration.
4. Deficiencies or malfunctions of citrate synthase can lead to metabolic disorders, affecting energy production and overall cellular function.
5. Citrate produced by citrate synthase can also be used for fatty acid synthesis or as a signaling molecule in various metabolic pathways.

Review Questions

• How does citrate synthase facilitate the integration of carbohydrate metabolism with energy production?
  • Citrate synthase plays a vital role by catalyzing the reaction between acetyl-CoA and oxaloacetate to form citrate, which is the first step of the citric acid cycle. This integration allows for the conversion of carbohydrates into energy through subsequent reactions in the cycle. By linking these pathways, citrate synthase ensures that the breakdown products of carbohydrates can efficiently enter energy-producing processes within cells.
• Discuss the regulatory mechanisms that control citrate synthase activity and their importance in metabolic pathways.
  • Citrate synthase activity is primarily regulated by substrate availability, particularly acetyl-CoA and oxaloacetate. When levels of these substrates are high, citrate synthase is activated, promoting the entry of carbon into the citric acid cycle. Additionally, feedback inhibition occurs when products such as citrate accumulate, signaling that energy needs are met. This regulatory balance is crucial for maintaining metabolic homeostasis and ensuring efficient energy production according to cellular demand.
• Evaluate the consequences of impaired citrate synthase function on cellular metabolism and overall organism health.
  • Impaired citrate synthase function can disrupt cellular metabolism by limiting the entry of acetyl-CoA into the citric acid cycle, resulting in reduced ATP production and energy deficiency. This dysfunction can lead to metabolic disorders and negatively impact various physiological processes. Additionally, an inability to properly regulate citrate levels may contribute to diseases such as obesity or diabetes, highlighting the enzyme's critical role in maintaining metabolic balance and organism health.

Related terms

Acetyl-CoA: A key molecule in metabolism that serves as a central metabolite in the citric acid cycle, derived from carbohydrates, fats, and proteins.

Oxaloacetate: A four-carbon molecule that combines with acetyl-CoA in the first step of the citric acid cycle, ultimately leading to the production of citrate.

Citric Acid Cycle: A series of enzymatic reactions that occur in the mitochondria, converting acetyl-CoA into CO2 and capturing energy in the form of ATP and electron carriers.