Question

The pyruvate dehydrogenase complex utilizes 5 cofactors:

for the listed cofactors describes briefly what its role is.

1. ATP

2. Lipoic acid

3.HSCoA

4.FAD

5. NAD+

Answer 1

Ans. Five coenzymes are used in the pyruvate dehydrogenase complex reactions:

1.TPP (Thiamine pyrophosphate)- Its role is to transfer of hydroxyethyl or “activated aldehyde” groups.The hydroxyethyl group of pyruvate oxidized to form an acetyl group and produce CO2 , then hydroxyethyl group transferred from TPP to lipomide to form acetyl lipomide.

2. Lipoic acid - It couples electron transfer to acyl group transfer.Lipoic acid forms acetyl lipomide which transfers its acetyl group to coenzyme A to produce acetyl CoA and reduced lipoic acid.

3..Coenzyme A - It involves in the reaction catalyzed by dihydrolipoyl transacetylase, and acts as a carrier of acyl groups to form acetyl CoA.

4.Flavin adenine dinucleotide -it participates in electron transfer, or hydride ion (:H– or H+ + 2e–) transfer. It receive hydride ion (:H– or H+ + 2e–) from reduced lipoic acid to produce oxidised lipoic acid and transfer hydride ion to NAD+.

5.Nicotinamide adenine dinucleotide - It participates in electron transfer, or hydride transfer by receiving electron or hydride from FADH and oxidize in electron chain reaction to produce ATP.