Biochemistry | Citrate Synthase Mechanism

The video discusses the mechanism of Citrate Synthase, an important enzyme in the Citric Acid cycle (TCA cycle). The mechanism involves two main steps: an Aldol Condensation followed by Hydrolysis.

Key Scientific Concepts and Mechanism Steps:

• Citrate Synthase Function: Catalyzes the conversion of Oxaloacetate and Acetyl-CoA into citrate.

Mechanism Overview:

• Aldol Condensation:
  • Involves the condensation of Oxaloacetate and Acetyl-CoA.
  • Requires a proton transfer that induces tautomerization of Acetyl-CoA.
  • The protonated histidine and deprotonated aspartate residues play crucial roles in the mechanism.
  • The tautomerization leads to the formation of an enol, which is unstable and drives the reaction forward.
  • The enol undergoes nucleophilic attack on the carbonyl of Oxaloacetate, forming a Citroyl-CoA intermediate.
• Hydrolysis:
  • The thioester bond in Citroyl-CoA is unstable and allows water to attack the carbonyl.
  • This generates a tetrahedral intermediate.
  • The carbonyl bond reforms, leading to the release of CoA and the formation of Citric Acid.
  • Citric Acid can lose a proton to exist as citrate at physiological pH.

Researchers or Sources Featured:

• No specific researchers or sources are mentioned in the video.