The order of prosthetic groups as they act in the three proteins of the PDH(pyruvate dehydrogenase)complex is:
A)FAD → thiamine pyrophosphate → NAD+
B)FAD → thiamine pyrophosphate → dihydrolipoamide
C)thiamine pyrophosphate → dihydrolipoamide → FAD
D)NAD+ → FAD → dihydrolipoamide

Question

Quizplus · Accepted Answer

The correct order of prosthetic groups as they act in the PDH complex is thiamine pyrophosphate (TPP) → dihydrolipoamide (DHLA) → FAD. TPP is responsible for decarboxylation of pyruvate, which yields a hydroxyethyl-TPP intermediate. The hydroxyethyl group is then transferred to the DHLA moiety of the dihydrolipoamide acetyltransferase (E2) subunit. The resulting acetyl-DHLA is then oxidized by FAD, which is located on the dihydrolipoamide dehydrogenase (E3) subunit. Finally, the electrons from FADH2 are transferred to NAD+ to form NADH, which is then used by the cell for ATP production. Therefore, option C is the best choice as it correctly lists the order of prosthetic groups in the PDH complex.

The Order of Prosthetic Groups as They Act in the Three