Question

The pyruvate dehydrogenase complex catalyzes the oxidative decarboxylation of pyruvate to form acetyl‑CoA. E 1 , E 2 , and E 3 are abbreviations for the enzymes of the complex. Classify the enzyme names, prosthetic groups, and reactions as E 1 , E 2 , or E 3 .

Answer 1

Answer:

E1: Pyruvate dehydrogenase, TPP, oxidative decarboxylation reaction

E2: Dihydrolipoyl transacetylase, Lipoamide and Co-enzyme A, transacetylation reaction.

E3: Dihydrolipoyl dehydrogenase, FAD and NAD+, oxidation reaction

Explanation:

Pyruvate dehydrogenase is a multi-enzyme complex with 5 co-enzymes and 3 apo-enzymes:

Pyruvate dehydrogenase (E1) , which uses thiamine pyrophosphate (TPP) as as co-enzymes to catalyze oxidative decarboxylation of pyruvate to hydroxyethyl-TPP.

Dihydrolipoyl transacetylase (E2): which uses lipoamide and coenzyme A as co-enzymes to catalyse the transacetylation from TPP to Lipoamide to form acetyl lipoamide.

Dihydrolipoyl dehydrogenase (E3)​​ which uses FAD and NAD+ as co-enzymes to catalyze the oxidation of lipoamide