Citrate synthase

Definition

Citrate synthase is an enzyme that catalyzes the first step of the citric acid cycle (Krebs cycle) by combining acetyl-CoA and oxaloacetate to form citrate. This reaction is crucial for cellular respiration, linking glycolysis and the Krebs cycle, which are both essential for energy production in cells.

5 Must Know Facts For Your Next Test

1. Citrate synthase is allosterically regulated, meaning its activity can be modulated by the binding of other molecules, ensuring the efficient flow of metabolites through the citric acid cycle.
2. The enzyme is found in the mitochondria, where it plays a key role in energy production by facilitating the conversion of energy substrates into usable forms.
3. Citrate produced by citrate synthase can serve as a precursor for various biosynthetic pathways, including fatty acid and cholesterol synthesis.
4. Deficiencies or mutations in citrate synthase can lead to metabolic disorders, highlighting its importance in maintaining metabolic balance.
5. The enzyme's activity is influenced by the concentrations of its substrates (acetyl-CoA and oxaloacetate) as well as inhibitors such as succinyl-CoA.

Review Questions

• How does citrate synthase link glycolysis to the Krebs cycle and why is this connection important for cellular respiration?
  • Citrate synthase links glycolysis to the Krebs cycle by using acetyl-CoA, which is generated from glycolysis, to produce citrate when it combines with oxaloacetate. This connection is vital because it enables the flow of carbon compounds from glycolysis into the Krebs cycle, allowing for continued energy production. This process ensures that cells can efficiently convert glucose into ATP while simultaneously generating important metabolic intermediates.
• Discuss the regulatory mechanisms that control citrate synthase activity and their significance for metabolic homeostasis.
  • Citrate synthase activity is controlled through allosteric regulation and feedback inhibition. Molecules such as NADH and succinyl-CoA can inhibit its activity when energy levels are high, preventing excessive production of citrate when it's not needed. This regulatory mechanism is significant for metabolic homeostasis as it ensures that energy production matches cellular demands, preventing imbalances that could lead to metabolic disorders.
• Evaluate the consequences of citrate synthase malfunction on overall cellular metabolism and energy production.
  • If citrate synthase malfunctions due to genetic mutations or enzyme deficiencies, it can severely disrupt overall cellular metabolism and energy production. The inability to produce citrate would halt the Krebs cycle, leading to reduced ATP generation and accumulation of glycolytic intermediates. This metabolic blockage could cause severe cellular dysfunction, impacting growth, reproduction, and overall organism health due to insufficient energy supply and imbalance in metabolite levels.

Related terms

Acetyl-CoA: A key molecule in metabolism that acts as a substrate for the citrate synthase reaction, formed from the breakdown of carbohydrates, fats, and proteins.

Oxaloacetate: A four-carbon molecule that reacts with acetyl-CoA in the presence of citrate synthase to produce citrate, playing a pivotal role in the citric acid cycle.

Krebs Cycle: A series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetate derived from carbohydrates, fats, and proteins.