Composition of Alpha keto Acid Dehydrogenase Multienzymatic Complexes


 

Original Question

 

Q (B-07): This is the enzyme of the Krebs cycle that is most similar to pyruvate dehydrogenase.

 

A (B-07): (b) Alpha-keto glutarate dehydrogenase

 

It is a multifunctional enzyme complex formed by the association of molecules of three different enzymes that participate directly in the reaction, and require five cofactors. 

 

Pyruvate Dehydrogenase Complex:

 

– E1: Pyruvate dehydrogenase (aka Pyruvate decarboxylase)

          Cofactor: TPP

– E2: Dihidrolipoyl transacetylase

          Cofactors: Lipoic acid; Co A

– E3: Dihydrolipoyl dehydrogenase

          Cofactors: FAD, NAD

 

Alphaketoglutarate Dehydrogenase complex:

 

-E1: Ketoglutarate dehydrogenase

        Cofactor: TPP

-E2: Dihydrolipoyl succinyl transferase

        Cofactors: Lipoic acid; Co A

-E3: Dihydrolipoyl dehydrogenase

        Cofactors: FAD, NAD

 

A very similar complex is the Branched chain alpha keto acid dehydrogenase complex. It results of association of molecules of the following enzymes and cofactors:  

 

-E1: Branched chain alphaketoacid dehydrogenase (aka branched chain alpha keto acid decarboxylase)

        Cofactor: TPP

-E2: Dihydrolipoyl transacylase (aka dihydrolipoyl acyltransferase)

       Cofactors: Lipoic acid; Co A

-E3: Dihydrolipoyl dehydrogenase

         Cofactors: FAD, NAD

 

Because of the presence of Lipoic acid in these complexes, they are affected by arsenic intoxication (see related posts: Question B-02 and Answer B-02)

 

  

Mutations in E1 or E2 of the Branched chain ketoacid dehydrogenase complex produces the Maple Syrup Urine Disease (Branched chain ketoaciduria), characterized by vomiting, convulsions, and early death or mental retardation in survivors (See related posts: Question P-01 and Answer P-01)

 

 

3 thoughts on “Composition of Alpha keto Acid Dehydrogenase Multienzymatic Complexes

  1. Pingback: A newborn with Maple Syrup Disease (P-01) « The Biochemistry Questions Site

  2. Pingback: Krebs Cycle Extended Matching Question « The Biochemistry Questions Site

  3. Pingback: Energetic Balance of the oxidation of 1 mol of Pyruvate up to CO2 and water « The Biochemistry Questions Site

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