Alpha oxidation is a process by which certain fatty acids are broken down by removal of a single carbon from the carboxyl end. In humans, alpha-oxidation is used in peroxisomes to break down dietary phytanic acid

Phytanic acid

Phytanic acid is a branched chain fatty acid that humans can obtain through the consumption of dairy products, ruminant animal fats, and certain fish. Western diets are estimated to provide 50-100 mg of phytanic acid per day...

, which cannot undergo beta-oxidation due to its β-methyl branch, into pristanic acid

Pristanic acid

Pristanic acid is a terpenoid acid present at micromolar concentrations in the blood plasma of healthy individuals. It is also found in the lipids from many sources such as freshwater sponges, krill, earthworms, whales, human milk fat, bovine depot fat, butterfat or Californian petroleum. It is...

, which can.

Pathway

Alpha-oxidation of phytanic acid

Phytanic acid

Phytanic acid is a branched chain fatty acid that humans can obtain through the consumption of dairy products, ruminant animal fats, and certain fish. Western diets are estimated to provide 50-100 mg of phytanic acid per day...

 is believed to take place entirely within peroxisomes.

1. Phytanic acid
   Phytanic acid
   Phytanic acid is a branched chain fatty acid that humans can obtain through the consumption of dairy products, ruminant animal fats, and certain fish. Western diets are estimated to provide 50-100 mg of phytanic acid per day...
   
    is first attached to CoA
   Coenzyme A
   Coenzyme A is a coenzyme, notable for its role in the synthesis and oxidation of fatty acids, and the oxidation of pyruvate in the citric acid cycle. All sequenced genomes encode enzymes that use coenzyme A as a substrate, and around 4% of cellular enzymes use it as a substrate...
   
    to form phytanoyl-CoA
   Phytanoyl-CoA
   Phytanoyl-CoA is a derivative of phytanic acid.-See also:* Phytanoyl-CoA hydroxylase...
   
   .
2. Phytanoyl-CoA
   Phytanoyl-CoA
   Phytanoyl-CoA is a derivative of phytanic acid.-See also:* Phytanoyl-CoA hydroxylase...
   
    is oxidized by phytanoyl-CoA dioxygenase
   Phytanoyl-CoA dioxygenase
   In enzymology, a phytanoyl-CoA dioxygenase is an enzyme that catalyzes the chemical reactionThe three substrates of this enzyme are phytanoyl-CoA, 2-oxoglutarate, and O2, whereas its three products are 2-hydroxyphytanoyl-CoA, succinate, and CO2....
   
   , in a process using Fe²⁺ and O₂, to yield 2-hydroxyphytanoyl-CoA.
3. 2-hydroxyphytanoyl-CoA is cleaved by 2-hydroxyphytanoyl-CoA lyase
   2-hydroxyphytanoyl-CoA lyase
   2-Hydroxyphytanoyl-CoA lyase is a peroxisomal enzyme involved in the catabolism of phytanoic acid by α-oxidation. It requires thiamine diphosphate as cofactor.It is classified under EC number 4.1.400px...
   
    in a TPP
   Thiamine pyrophosphate
   Thiamine pyrophosphate , or thiamine diphosphate , is a thiamine derivative which is produced by the enzyme thiamine pyrophosphatase. Thiamine pyrophosphate is a coenzyme that is present in all living systems, in which it catalyzes several biochemical reactions...
   
   -dependent reaction to form pristanal and formyl-CoA (in turn later broken down into formate
   Formate
   Formate or methanoate is the ion CHOO− or HCOO− . It is the simplest carboxylate anion. It is produced in large amounts in the hepatic mitochondria of embryonic cells and in cancer cells by the folate cycle Formate or methanoate is the ion CHOO− or HCOO− (formic acid minus one hydrogen ion). It...
   
    and eventually CO₂).
4. Pristanal is oxidized by aldehyde dehydrogenase
   Aldehyde dehydrogenase
   Aldehyde dehydrogenases are a group of enzymes that catalyse the oxidation of aldehydes.- Function :Aldehyde dehydrogenase is a polymorphic enzyme responsible for the oxidation of aldehydes to carboxylic acids, which leave the liver and are metabolized by the body’s muscle and heart...
   
    to form pristanic acid
   Pristanic acid
   Pristanic acid is a terpenoid acid present at micromolar concentrations in the blood plasma of healthy individuals. It is also found in the lipids from many sources such as freshwater sponges, krill, earthworms, whales, human milk fat, bovine depot fat, butterfat or Californian petroleum. It is...
   
    (which can then undergo beta-oxidation).

(Propionyl-CoA is released as a result of beta oxidation when the beta carbon is substituted)

Deficiency

Enzymatic deficiency in alpha-oxidation (most frequently in phytanoyl-CoA dioxygenase

Phytanoyl-CoA dioxygenase

In enzymology, a phytanoyl-CoA dioxygenase is an enzyme that catalyzes the chemical reactionThe three substrates of this enzyme are phytanoyl-CoA, 2-oxoglutarate, and O2, whereas its three products are 2-hydroxyphytanoyl-CoA, succinate, and CO2....

) leads to Refsum's disease

Refsum's disease

Refsum disease, also known as classic or adult Refsum disease, heredopathia atactica polyneuritiformis, phytanic acid oxidase deficiency and phytanic acid storage disease, is an autosomal recessive neurological disease that results from the over-accumulation of phytanic acid in cells and tissues...

, in which the accumulation of phytanic acid

Phytanic acid

Phytanic acid is a branched chain fatty acid that humans can obtain through the consumption of dairy products, ruminant animal fats, and certain fish. Western diets are estimated to provide 50-100 mg of phytanic acid per day...

 and its derivatives leads to neurological damage. Other disorders of peroxisome

Peroxisome

Peroxisomes are organelles found in virtually all eukaryotic cells. They are involved in the catabolism of very long chain fatty acids, branched chain fatty acids, D-amino acids, polyamines, and biosynthesis of plasmalogens, etherphospholipids critical for the normal function of mammalian brains...

biogenesis also prevent alpha-oxidation from occurring.