Metabolism Anthony Baines Flashcards
What occurs to the pyruvate produced by glycolysis?
- Is oxidised to acetyl-CoA and CO2 in an oxidative decarboxylation reaction
What occurs in the oxidative decarboxylation reaction?
1) Carboxyl group removed from pyruvate as a molecule of CO2 and 2 remaining carbons becoming acetyl group of acetyl-CoA
2) NADH formed gives up a hydride ion (:H-) to the respiratory chain
What is the pyruvate dehydrogenase complex?
A complex of enzymes that convert pyruvate into acetyl-CoA and CO2
What are the names of the 3 enzymes used in the complex?
E1 - pyruvate dehydrogenase
E2 - dihydrolipoyl transacetylase
E3 - dihydrolipoyl dehydrogenase
What are the names of the 5 cofactors/prosthetic groups involved in the PDC?
- Thiamine pyrophosphate (TPP)
- Flavin adenine dinucleotide (FAD)
- Coenzyme-A (CoA-SH)
- Nicotinamide adenine dinucleotide (NAD)
- Lipoate
What 4 vitamins are vital components of 4 of the cofactors?
B1 in TPP
B2 in FAD
B3 in NAD
B5 in CoA
What is the role of FAD and NAD?
Electron carriers
What is the role of TPP?
TPP is a coenzyme of pyruvate decarboxylase
What makes coenzyme A a good candidate for acyl group transfer?
- Has a reactive thiol group (-SH)
- Acyl groups covalently linked to thiol groups, forming thioesters
- Thioesters have high acyl transfer potential
Why is lipoate an important molecule?
Has 2 thiol groups that can undergo reversible oxidation to a disulphide bond (-S-S-)
- can serve as both electron and acyl carrier
What is the overall reaction catalysed by the pyruvate dehydrogenase complex?
Pyruvate + CoA-SH + NAD+ ——–> Acetyl-CoA + NADH + CO2 (TPP, Lipoate
FAD, E1,2+3)
What is the diameter of the PDC in mammals?
50nm
Describe the reaction mechanism of the PDC
1) Pyruvate reacts with bound TPP of E1, undergoing decarboxylation to hydroxyethyl derivative
2) Hydroxyethyl is oxidised to
