Citric Acid cycle orTricarboxylic Acid cycle or Krebs Cycle
Citric Acid cycle Step-1: conversion of pyruvic acid to acetyl-CoA
Conversion of pyruvic acid into acetyl-CoA
Reactions of Citric Acid Cycle3. Citrate synthase: Formation of Citric acid
2. Aconitase: This enzyme catalyses the isomerization reaction byremoving and then adding back the water ( H and OH ) to cis-aconitatein at different positions. Isocitrate is consumed rapidly by the nextstep thus deriving the reaction in forward direction.
3. Isocitrate dehydrogenase: There are two isoforms of this enzyme,one uses NAD+ and other uses NADP+
4. α-Ketoglutarate dehydrogenase:
5. Succinyl CoA synthatse: Sccinyl CoA, like Acetyl CoA has athioester bond. In this reaction, the hydrolysis of the thioester bondleads to the formation of phosphoester bond with inorganicphosphate. This phosphate is transferred to Histidine residue of theenzyme and this high energy, unstable phosphate is finallytransferred to GDP resulting in the generation of GTP.
6. Succinate Dehydrogenase: Oxidation of succinate to fumarate. It isan FAD dependent enzyme.
7. Fumarase: Hydration of Fumarate to malate: It is a highlystereospecific enzyme.
8. L-Malate dehydrogenase: Oxidation of malate to oxaloacetate: It is anNAD+dependent enzyme.