Biochem Lecture 19- TCA (incomplete)

What processes can feed into TCA?

Those that make acetyl CoA- glycolysis, fatty acid beta-oxidation, and amino acid oxidative deamination.

What is the equation for TCA? What is the delta G?

Acetyl-CoA + 3NAD+ + FAD + ADP + Pi - 2H2O > 2CO2 + 3NADH + 3H + FADH2 + ATP + CoA. -40kJ/mol.

What 3 enzymes make up pyruvate dehydrogenase complex?

Pyruvate dehydrogenase, dihydrolipoyl transacetylase, and dihydrolipoyl dehydrogenase.

What is the equation for pyruvate dehydrogenase?

Pyruvate + CoA + NAD+ > acetyl-CoA + CO2 + NADH

What 5 coenzymes are used for pyruvate dehydrogenase?

Thiamine pyrophosphate (needs thiamine/B1), Lipoic acid, CoA, NAD+, FAD.

What is a thiamine deficiency? What other disease does it share symptoms with?

Beriberi- weight loss, weakness and pain, emotional and sensory issues, heart rate issues, edema. Arsenite and mercury poisoning (inhibit PDC).

What is the fate of the carboxyl carbon on acetyl-CoA?

Lost after 2 turns.

What is the fate of the methyl carbon of acetyl-CoA?

Becomes more diluted with each turn.

How is PDC regulated? How is it allosterically controlled?

Phosphorylation by ATP deactivates it, phosphatase uses water to dephosphorylate it to make it active again. ADP and pyruvate (low energy) positively regulate it. ATP, Acetyl CoA, and NADH (high energy) negatively regulate it.

How does adrenaline regulate PDC?

In the liver it interacts with the alpha adrenergic receptor which activates phosphatase which activates PDC.

When are there chiral molecules in the TCA cycle?

Isocitrate

What does flouroacetate do?

It is turned into fluoroacetyl-CoA by acetyl-CoA synthase (alternative to PDC) which is then made into fluorocitrate by citrate synthesis and is ver poisonous.

How is a-ketoglutarate dehydrogenase similar to PDC?

3 enzyme complex that uses the same coenzymes.

What TCA enzymes are soluble in the mitochondrial matrix?

All except succinate dehydrogenase which is an integral membrane protein on the inner mitochondrial matrix (has other functions in the ETC).

What intermediate TC products can be used as precursors?

Citrate- fatty acids and sterols. a-ketoglutarate- glutamine, then other amino acids, then purines. Succinyl CoA- polyphyrins, heme, chlorophyll. Oxaloacetate- glucose, aspartate to other amino acids, purines, and pyrimidines.

What reactions replenish TCA intermediates?

Pyruvate carboxylase- pyruvate + CO2 + ATP > ADP + P + Oxaloacetate.
PEP carboxylase- PEP + H2O + CO2 > P + oxaloacetate.
Malic enzyme- pyruvate + H+ + NADPH + CO2 > NADP+ + L-malate.