ω-oxidation

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The ω-oxidation is a special variant of the fatty acid breakdown ( β-oxidation ). In this case, a carboxy group is introduced to the carbon atom (C ω ) of a fatty acid with a medium chain length (10 to 12 carbon atoms) which is the furthest away from the originally present carboxy group. The resulting dicarboxylic acid is then further metabolized.

In vertebrates (including humans), the initial reaction is carried out in the endoplasmic reticulum of the liver or kidney cells , while the subsequent oxidations to carboxylic acid take place in the cytoplasm .

biochemistry

Introducing a carboxy group requires several steps:

1. Introduction of a hydroxyl group at the C ω atom
Omega-oxidation 1 de.svg
The ω-oxidation begins with the introduction of a hydroxyl group to the C ω -atom (= terminal methyl group ). A monooxygenase, cytochrome P450 , and NADPH as a coenzyme are required for this reaction . Reactions of this type are catalyzed by enzymes with a mixed function ( EC  1.14.15.3 ). When oxygen is consumed, the hydroxylated fatty acid ( 2 ) is formed as well as water and NADP + .
2. Oxidation of the hydroxyl group to the aldehyde group
Omega-oxidation 2 de.svg
In the cytosol, an alcohol dehydrogenase catalyzes the oxidation of the hydroxyl group to the aldehyde ( 3 ).
3. Oxidation of the aldehyde group to the carboxy group
Omega-oxidation 3 de.svg
The aldehyde group is finally oxidized to the carboxy group ( 4 ), which catalyzes an aldehyde dehydrogenase.

The resulting dicarboxylic acid is esterified with coenzyme A on both sides . This is then broken down into a shorter-chain dicarboxylic acid in the β-oxidation in the mitochondria . This produces either succinic acid ( succinate , C 4 ) or adipic acid (C 6 ). However, this process can also take place in the peroxisomes .

meaning

With regard to fatty acid degradation by means of regular β-oxidation, ω-oxidation plays a subordinate role, but if the former cannot proceed correctly, ω-oxidation becomes more important.

See also

Individual evidence

  1. ^ A b c d Albert Lehninger, Michael Cox, and David L. Nelson: Lehninger Principles of Biochemistry . WH Freeman & Co; 5th edition 2008; ISBN 978-0-7167-7108-1 ; P. 664.
  2. ↑ a b Thomas M. Devlin (Ed.): Textbook of Biochemistry with Clinical Correlations . Wiley & Sons; 6th edition 2005; ISBN 978-0-471-67808-3 ; P. 686f.

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