𝜶-oxidation of fatty acids:
𝜶-oxidation of fatty acids are specialized pathways. α –oxidation of fatty acids is the removal of one carbon at a time from the carboxyl end of the molecule that has been detected in brain tissue.
It does not give rise to CoA intermediates and does not generate high-energy phosphates.
It is mainly utilized for the fatty acids that have a methyl group at β–carbon, which blocks β–oxidation of fatty acid (Phytanic acid-a major dietary methylated fatty acid present in chlorophyll, milk, & animal fats).
The α-oxidation of a branched-chain fatty acid (Phytanic acid). Phytanic acid cannot go through β oxidation first. It undergoes a-oxidation to remove the α–carbon as CO2& this is followed by α –oxidation fatty acid.
Refsum disease was first identified as a distinct disease entity by Sigvald Refsum in the 1940s. It is also known as Phytanate storage disease.
It is a rare neurologic inborn error of lipid metabolism. It occurs due to inherited defects in α-oxidation of fatty acids.
It is caused due to genetic deficiency in the enzyme phytanoyl CoA hydroxylase (phytanic acid α-oxidase). Inability to metabolize phytanic acid which is a branched-chain fatty acid). Accumulation of large quantities of phytanic acid occurs.
Clinical symptoms include retinitis pigmentosa (progressive degeneration of retina), peripheral neuropathy, and ataxia.
It is treated with a diet that contains low in phytol and phytanic acid (no green leafy vegetables, animal fats, or milk products).
Omega oxidation of fatty acid:
It occurs in the endoplasmic reticulum (liver and kidney). The ω-oxidation is a minor pathway and is brought about by cytochrome P450in the endoplasmic reticulum.
In this, the fatty acids are oxidized at the ω-carbon of the chain via. a series of enzymes. The CH3group (e.g.Lauric acid) is converted to a -CH2OH group that subsequently is oxidized to -COOH, thus forming a dicarboxylic acid.
They subsequently undergo ß-oxidation and are excreted in the urine. The ω- oxidation becomes important when beta-oxidation is defective. The short-chain dicarboxylic acid such as pimelic acid, a precursor of biotin formed by omega oxidation.