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 crucial step in energy production, linking carbohydrate, fat, and protein metabolism to ATP synthesis through oxidative phosphorylation.

5 Must Know Facts For Your Next Test

1. Citrate synthase is allosterically regulated by the concentration of its substrates and products, ensuring a balance in the citric acid cycle.
2. The enzyme is found in the mitochondria of eukaryotic cells, where it plays a vital role in energy metabolism.
3. Citrate synthase has a significant impact on metabolic pathways beyond the citric acid cycle, including fatty acid synthesis and gluconeogenesis.
4. The reaction catalyzed by citrate synthase is irreversible under physiological conditions, which helps drive the cycle forward.
5. Citrate synthase can be inhibited by high levels of ATP and NADH, reflecting the energy status of the cell and helping to regulate overall metabolism.

Review Questions

• How does citrate synthase contribute to the overall function of the citric acid cycle?
  • Citrate synthase initiates the citric acid cycle by catalyzing the formation of citrate from acetyl-CoA and oxaloacetate. This first step is critical as it not only starts the cycle but also ensures that incoming acetyl-CoA is efficiently processed for energy production. The activity of citrate synthase directly influences the flow of metabolites through the citric acid cycle, which is vital for generating ATP and reducing equivalents.
• What mechanisms regulate citrate synthase activity and how do they impact cellular metabolism?
  • Citrate synthase is regulated through allosteric mechanisms, where its activity is influenced by the concentrations of substrates like acetyl-CoA and oxaloacetate, as well as products such as citrate. Inhibitors like ATP and NADH signal high energy status within the cell, reducing enzyme activity when energy is plentiful. This regulation ensures that citrate synthase functions optimally according to cellular energy needs, impacting overall metabolism and homeostasis.
• Evaluate the consequences of malfunctioning citrate synthase on metabolic processes within cells.
  • If citrate synthase malfunctions or exhibits decreased activity, it can lead to a bottleneck in the citric acid cycle. This disruption would impair energy production through ATP synthesis, ultimately affecting cellular respiration. Reduced levels of citrate could also influence fatty acid synthesis and gluconeogenesis pathways, leading to potential metabolic disorders or imbalances in nutrient processing. Overall, the proper functioning of citrate synthase is crucial for maintaining metabolic health.

Related terms

Acetyl-CoA: A central metabolic intermediate that serves as a key substrate for various biochemical reactions, including the citric acid cycle.

Oxaloacetate: A four-carbon compound that combines with acetyl-CoA in the first step of the citric acid cycle, forming citrate.

Citric Acid Cycle: Also known as the Krebs cycle, it is a series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetyl-CoA.