{{

TRICARBOXYLIC TRICARBOXYLIC ACID CYCLEACID CYCLE

Yhong Alderite ,MSERMYhong Alderite ,MSERM

STEP 1: CITRATE SYNTHASE

Process:

1. Formation of citric acid

2. Dehydration

Enzyme: citrate synthase

Step 2: Aconitase Reaction

Process : Hydration

Enzyme: Aconitase

Step 3: Isocitrate Dehydrogenase Rxn

Process:

1. Dehydrogenation I 

2. Decarboxylation

Enzyme: isocitrate dehydrogenase

Step 4: a-Ketoglutarate Dehydrogenase Rxn

Process: Oxidative decarboxylation

Enzyme: a-ketoglutarate dehydrogenase

Step 5: Succinyl Co A Synthetase Rxn

Process:Oxidative decarboxylation

Enzyme: Succinyl-CoA synthetase

Step 6 : Succinate Dehydrogenase Rxn

Process: Oxidation

Enzyme: succinate dehydrogenase

Step 7: Fumarase Rxn

Process: Hydration

Enzyme: Fumarase

Step 8: Malate Dehydrogenase Rxn

Process: Dehydrogenation

Enzyme: malate dehydrogenase

Three control points within the cycleThree control points within the cycle

– – citrate synthase, isocitrate dehydrogenase, and a -citrate synthase, isocitrate dehydrogenase, and a -ketoglutarate dehydrogenase, are the rate limiting and ketoglutarate dehydrogenase, are the rate limiting and regulatory enzymes of the citric acid cycle.regulatory enzymes of the citric acid cycle.

One control point outside the cycleOne control point outside the cycle

– – The decarboxylation of pyruvate to acetyl-CoA is The decarboxylation of pyruvate to acetyl-CoA is irreversible.Therefore, it is critical that the reaction be irreversible.Therefore, it is critical that the reaction be regulated.regulated.

Summary of Materials and Products:Summary of Materials and Products:

Needed Materials:Needed Materials: Products:Products:

-Pyruvate -Pyruvate - 3 CO- 3 CO22

-4NAD -4NAD - 4NADH- 4NADH

-FAD -FAD - FADH- FADH22

-GDP -GDP - GTP- GTP

-Pi-Pi - 4H+- 4H+

-2 H-2 H22OO

TCA and Amino Acid SynthesisTCA and Amino Acid Synthesis

TCA and Fatty Acid Synthesis

TCA and TCA and GluconeogenesisGluconeogenesis

TCA cycle in TCA cycle in catabolismcatabolism