Question

Coenzyme A serves as a carrier of activated acetyl or acyl group. Key enzymes involving Coenzyme A are:
A. Pyruvate dehydrogese
B. $\alpha$- Ketoglutarate dehydrogese
C. Thiokise
D. Glyceraldehyde 3 phosphate dehydrogese

• A. B, C and D Only
• B. A, C and D Only
• C. A, B and C Only
• D. A, B and D Only

Hint:

Coenzyme A (CoA-SH) participates in thioester bond formation:
1. Pyruvate Dehydrogese $\to$ Forms Acetyl-CoA.
2. $\alpha$-Ketoglutarate Dehydrogese $\to$ Forms Succinyl-CoA.
3. Thiokise $\to$ Forms Acyl-CoA Succinyl-CoA.
GAPDH uses inorganic phosphate ($\text{P}_i$), NOT Coenzyme A!

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks to identify which of the listed metabolic enzymes utilize Coenzyme A (CoA-SH) as a required cofactor/substrate to carry acyl or acetyl groups.

Step 2: Key Formula or Approach:
Coenzyme A contains a termil thiol ($-SH$) group that reacts with carboxylic acids to form high-energy thioester bonds (e.g., Acetyl-CoA, Succinyl-CoA, Fatty Acyl-CoA).

Step 3: Detailed Explation:

• A. Pyruvate Dehydrogese Complex (PDH): Converts pyruvate into acetyl-CoA via oxidative decarboxylation, utilizing CoA-SH as a termil acceptor substrate. Thus, A is correct.

• B. $\alpha$-Ketoglutarate Dehydrogese Complex: Converts $\alpha$-ketoglutarate into succinyl-CoA in the TCA cycle, requiring CoA-SH. Thus, B is correct.

• C. Thiokise (Acyl-CoA Synthetase Succinyl-CoA Synthetase): Catalyzes the activation of fatty acids to acyl-CoA or the cleavage/formation of succinyl-CoA using CoA. Thus, C is correct.

• D. Glyceraldehyde-3-Phosphate Dehydrogese (GAPDH): Glycolytic enzyme that oxidizes glyceraldehyde-3-phosphate using inorganic phosphate ($\text{P}_i$) and $\text{D}^+$ to yield 1,3-bisphosphoglycerate without involving Coenzyme A. Thus, D is incorrect.

Step 4: Fil Answer:
Enzymes A, B, and C utilize Coenzyme A, making Option (C) correct.