Omega Oxidation of Fatty Acids

What are Fatty Acids?

Fatty acids are important biological molecules that are made up of carboxylic acid with an aliphatic chain. They can either be saturated or unsaturated. They not only act as a source of high energy but are also chief components of phospholipids, cholesterol ester, and glycolipids that make up the biomembranes.

Pathways of Fatty Acid Oxidation

There are three pathways known for the oxidation of fatty acids:

1. β-oxidation: This is the most common pathway of fatty acid oxidation. Fatty acids are broken into acetyl CoA, which is then converted into carbon dioxide and water, resulting in energy production. It takes place in the peroxisomes.
2. ɑ-oxidation: In this pathway, single carbon atoms are removed from the carboxyl end. This pathway is important for the oxidation of phytanic acids because they have a methyl group that blocks β-oxidation. ɑ-oxidation of fatty acids removes the methyl group, after which β-oxidation takes over.
3. ⍵-oxidation: It is an alternative pathway to β-oxidation that takes place in some animals. Read this article to know more about ⍵-oxidation.

Steps of Omega Oxidation

Omega (⍵) oxidation is an alternative pathway to β-oxidation that takes place in the smooth endoplasmic reticulum of the kidney and liver in vertebrates. It is a minor pathway that produces dicarboxylic fatty acids from medium chain fatty acids. This pathway becomes important when the pathway for β-oxidation is defective. It is a three-step process which is as follows:

• Hydroxylation: In the first step, a hydroxyl group is introduced at the ⍵ carbon (the carbon farthest away from the carboxyl group). The oxygen for this addition arises from the complex cytochrome P450, and the electron donor is NADPH. It takes place in the presence of enzyme mixed function oxidase.
• Oxidation: In the second step, the hydroxyl group is oxidised into an aldehyde by alcohol dehydrogenase. In the process, NAD⁺ is converted into NADH.
• Oxidation: In the third and last step, the aldehyde is oxidised into carboxylic acid by aldehyde dehydrogenase. In the end, a dicarboxylic fatty acid is produced.

Acetyl CoA can now attach to either end of the fatty acid, get transported to the mitochondria, and undergo β-oxidation.

Biological Significance of Omega Oxidation

It is a minor pathway that serves as an important alternative to defective β-oxidation pathways. Some studies have shown that omega oxidation can form glucose from succinyl-CoA in times of starvation and diabetes. It is an important pathway for the production of pheromones in honeybees and biopolyesters in higher plants.

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Also Read:

• What are Lipids? – Definition, Structure & Classification of Lipids
• Importance of Fats – Types of Fats, Sources and Its Benefits