Summary of "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.

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.