Pyruvate (AAAGH)

E1

Enzyme that uses TPP to catalyze the decarboxylation of an alpha ketoacid/pyruvate.

E2

Dihydrolipoamide transacetylase that transfers the acetyl group to Coenzyme A.

E3

Dihydrolipoamide dehydrogenase that reoxidizes lipoamide and generates NADH.

TPP

Thiamine pyrophosphate; a cofactor that catalyzes decarboxylation of pyruvate.

Lipoic acid (lipoamide)

An acyl transfer and electron carrier, crucial for the function of E2.

CoA

Coenzyme A; accepts the acetyl group from acetyllipoamide to form Acetyl CoA.

FAD

Flavin adenine dinucleotide; accepts electrons in E3 during the reoxidation of lipoamide.

NAD+

Final electron acceptor in E3 that is reduced to NADH.

Pyruvate Dehydrogenase Kinase

Enzyme that phosphorylates and inactivates the PDH complex.

Activators of Pyruvate Dehydrogenase Kinase

NADH and AcetylCoA, which turn off the PDH complex.

Inactivators of Pyruvate Dehydrogenase Kinase

Pyruvate, which activates the PDH complex.

What does phosphorylation of E1 do?

It inactivates the PDH complex.

What are the activators of Pyruvate Dehydrogenase Phosphatase?

Ca2+ and insulin signaling via cascade.

What are the inactivators of Pyruvate Dehydrogenase Phosphatase?

High NADH and high Acetyl CoA.

How does PD Phosphatase affect phosphorylation of E1?

Dephosphorylation of E1 activates the PDH complex.

Step 1 in E1

Decarboxylation of alpha ketoacid/pyruvate forming hydroxyethyl-TPP intermediate.

Step 2 in E1

Oxidation of hydroxyethyl-TPP and transfer to lipoamide to form acetyllipoamide.

Step 3 in E2

E2 catalyzes the transfer of the acetyl group to Coenzyme A, producing Acetyl CoA.

Step 4 in E3

Oxidation of lipoamide to regenerate lipoamide by reducing FAD to FADH2.

Step 5 in E3

Transfer of electrons from FADH2 to NAD+, generating FAD and NADH.

What is a key function of lipoic acid in E2?

Acts as an acyl transfer and electron carrier.