Question

Match List-I with List-II

List-I (Name of the enzyme) & List-II (Role in the fatty acid oxidation)
(A) 2,4-dienoyl-CoA reductase & (I) Involved in the $\alpha$-oxidation of branched fatty acids
(B) Phytanoyl- CoA hydroxylase & (II) Involved in the oxidation of unsaturated fatty acids
(C) Acyl-CoA oxidase & (III) Involved in the $\omega$-oxidation of medium chain fatty acids
(D) Cytochrome P450 & (IV) Involved in the peroxisomal $\beta$-oxidation

• (A) - (I), (B) - (II), (C) - (III), (D) - (IV)
• (A) - (III), (B) - (II), (C) - (I), (D) - (IV)
• (A) - (II), (B) - (I), (C) - (IV), (D) - (III)
• (A) - (III), (B) - (IV), (C) - (I), (D) - (II)

Hint:

A genetic deficiency in the enzyme Phytanoyl-CoA hydroxylase leads to Refsum disease, a neurological disorder characterized by the toxic accumulation of phytanic acid in tissues.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Fatty acid catabolism occurs through several distinct oxidative pathways depending on the structure, branching, and chain length of the fatty acids.
These pathways include mitochondrial $\beta$-oxidation, peroxisomal $\beta$-oxidation, peroxisomal $\alpha$-oxidation, and endoplasmic reticulum $\omega$-oxidation.

Step 2: Detailed Explanation:
Let us analyze the role of each enzyme in fatty acid oxidation:
1. 2,4-dienoyl-CoA reductase: This is an auxiliary enzyme required for the $\beta$-oxidation of unsaturated fatty acids containing double bonds at even-numbered carbon positions.
It uses NADPH to reduce a 2,4-dienoyl-CoA intermediate to a trans-3-enoyl-CoA intermediate, which is then converted by an isomerase into a standard $\beta$-oxidation substrate.
Thus, (A) matches with (II).
2. Phytanoyl-CoA hydroxylase: This enzyme catalyzes the first step of $\alpha$-oxidation of phytanic acid, a branched-chain fatty acid derived from the phytol side-chain of chlorophyll.
This pathway is essential because the methyl branch at the $\beta$-carbon of phytanic acid blocks standard $\beta$-oxidation.
Thus, (B) matches with (I).
3. Acyl-CoA oxidase: This is the first enzyme of the peroxisomal $\beta$-oxidation pathway.
Unlike the mitochondrial equivalent (acyl-CoA dehydrogenase), it transfers electrons from fatty acyl-CoA directly to molecular oxygen, producing hydrogen peroxide ($\text{H}_2\text{O}_2$).
Thus, (C) matches with (IV).
4. Cytochrome P450: This enzyme family catalyzes the hydroxylase step of $\omega$-oxidation in the endoplasmic reticulum.
This pathway oxidizes the terminal methyl ($\omega$) carbon of medium-to-long chain fatty acids to a dicarboxylic acid, serving as an alternative pathway when $\beta$-oxidation is compromised.
Thus, (D) matches with (III).
This gives the match combination: (A) - (II), (B) - (I), (C) - (IV), (D) - (III).

Step 3: Final Answer:
The correct matching sequence is (A) - (II), (B) - (I), (C) - (IV), (D) - (III), which corresponds to option (C).