Question

The sequence for the action of the following enzymes of fatty acid \(\beta\)-oxidation pathway is:
(A). \(\beta\)-hydroxyacyl-CoA dehydrogenase
(B). Thiolase
(C). Enoyl CoA hydratase
(D). Acyl CoA - dehydrogenase
Choose the correct answer from the options given below:

• A. (A), (B), (C), (D).
• B. (B), (C), (A), (D).
• C. (D), (C), (A), (B).
• D. (C), (B), (D), (A).

Hint:

An easy way to remember the sequence of reactions in \(\beta\)-oxidation is the acronym OHOT: Oxidation, Hydration, Oxidation, Thiolysis.
This corresponds to Acyl-CoA dehydrogenase, Enoyl-CoA hydratase, \(\beta\)-hydroxyacyl-CoA dehydrogenase, and Thiolase.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Beta-oxidation is a key pathway in fatty acid catabolism, composed of four recurring chemical reactions that shorten the acyl chain by two carbon units at a time.

Step 2: Detailed Explanation:
Let us trace the four steps of the cycle:
1. Oxidation: The enzyme Acyl-CoA dehydrogenase (D) oxidizes the fatty acyl-CoA to form a double bond between the \(\alpha\) and \(\beta\) carbons, producing trans-\(\Delta^2\)-enoyl-CoA.
2. Hydration: The enzyme Enoyl-CoA hydratase (C) adds a water molecule across the double bond of trans-\(\Delta^2\)-enoyl-CoA to yield L-\(\beta\)-hydroxyacyl-CoA.
3. Oxidation: The enzyme \(\beta\)-hydroxyacyl-CoA dehydrogenase (A) oxidizes the hydroxyl group on the \(\beta\) carbon to a keto group, generating \(\beta\)-ketoacyl-CoA.
4. Thiolysis: The enzyme Thiolase (B) cleaves the \(\beta\)-ketoacyl-CoA to release a molecule of acetyl-CoA and a shortened fatty acyl-CoA chain.
The correct order of action is (D) \(\rightarrow\) (C) \(\rightarrow\) (A) \(\rightarrow\) (B).

Step 3: Final Answer:
This sequence matches option (C).