Pyruvate dehydrogenase complex

Question 1

Location, function, condition

Answer 1

• mitochondrial matrix
• catalyzes irreversible oxidative carboxylation of pyruvate to acetyl CoA
• aerobic

Question 2

Enzymes

Answer 2

metabolic:
-E1: pyruvate decarboxylase
-E2: dihydrolipoyl transacetylase
-E3: dihydrolipoyl dehydrogenase
regulatory:
-PDH kinase( inactivates PDHC)
-PDH phosphatase( Activates by phosphorylating E1)

Question 3

First reaction of PDHC

Answer 3

pyruvate + thioamine pyrophosphate(TPP) + H+ -> Hydroxyethylthioamine pyrophosphate (HETPP) + CO2

• TPP produced from ATP and vitamin thiamine
• enzyme: PYRUVATE DECARBOXYLASE

Question 4

Second reaction of PDHC

Answer 4

Hydroxyethylthioamine pyrophosphate + Lipoamide -> Acetyl-dihydrolipoamide + Thioamine pyrophosphate carboanion
-enzyme: DIHYDROLIPOYL TRANSFERASE

Question 5

Third reaction of PDHC

Answer 5

Acetyl-dihydrolipoamide + SH-CoA -> Acetyl CoA + dihydrolipoamide

• acetyl CoA used in TCA or lipid biosynthesis
• enzyme: DIHYDROLIPOYL TRANSFERASE

Question 6

Fourth reaction of PDHC

Answer 6

Dihydrolipoamide + FAD -> Lipoamide + FADH2

-enzyme: DIHYDROLIPOYL DEHYDROGENASE

Question 7

Allosteric regulation (of kinase that inactivates PDH)

Answer 7

phosphorylated (inactive) / dephosphorylated (active)
\+ NADH
\+ acetyl CoA
\+ pyruvate
- NAD+
- SH-CoA
- ADP

• Covalent modification
• Arsenic

Question 8

PDHC diseases

Answer 8

• Beriberi
• E1/E2 defect
• E3 defect

Question 9

Acetyl CoA

Answer 9

• acyl carrier
• derived from pantothenic acid
• production-energy dependent process(G=-32,5kJ/mol)

Question 10

Transport of Acetyl CoA through inner mitochondrial membrane

Answer 10

1. Carnitine acyltransferase 1

2. Carnitine acyltransferase 2