Omega oxidation
Encyclopedia
Omega oxidation is a process of fatty acid metabolism
in some species of animals. It is an alternative pathway to beta oxidation
that, instead of involving the β carbon, involves the oxidation of the ω carbon (the carbon most distant from the carboxyl group of the fatty acid). The process is normally a minor catabolic pathway for medium-chain fatty acids (10-12 carbon atoms), but becomes more important when β oxidation is defective.
In vertebrates, the enzymes for ω oxidation are located in the endoplasmic reticulum
of liver
and kidney
cells, instead of in the mitochondria as with β oxidation. The steps of the process are as follow:
After the three steps, either end of fatty acid can be attached to coenzyme A
. The molecule can enter the mitochondrion and undergo β oxidation. The final products after successive oxidation include succinic acid
, which can enter citric acid cycle
, and adipic acid
.
Fatty acid metabolism
Fatty acids are an important source of energy and adenosine triphosphate for many cellular organisms. Excess fatty acids, glucose, and other nutrients can be stored efficiently as fat. Triglycerides yield more than twice as much energy for the same mass as do carbohydrates or proteins. All cell...
in some species of animals. It is an alternative pathway to beta oxidation
Beta oxidation
Beta oxidation is the process by which fatty acids, in the form of Acyl-CoA molecules, are broken down in mitochondria and/or in peroxisomes to generate Acetyl-CoA, the entry molecule for the Citric Acid cycle....
that, instead of involving the β carbon, involves the oxidation of the ω carbon (the carbon most distant from the carboxyl group of the fatty acid). The process is normally a minor catabolic pathway for medium-chain fatty acids (10-12 carbon atoms), but becomes more important when β oxidation is defective.
In vertebrates, the enzymes for ω oxidation are located in the endoplasmic reticulum
Endoplasmic reticulum
The endoplasmic reticulum is an organelle of cells in eukaryotic organisms that forms an interconnected network of tubules, vesicles, and cisternae...
of liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
and kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
cells, instead of in the mitochondria as with β oxidation. The steps of the process are as follow:
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Reaction >- | Hydroxylation Hydroxylation Hydroxylation is a chemical process that introduces a hydroxyl group into an organic compound. In biochemistry, hydroxylation reactions are often facilitated by enzymes called hydroxylases. Hydroxylation is the first step in the oxidative degradation of organic compounds in air... |
mixed function oxidase Mixed function oxidase Mixed-function oxidase is the name of a family of oxidase enzymes that catalyze a reaction in which each of the two atoms of oxygen in O2 is used for a different function in the reaction.... |
The first step introduces a hydroxyl group onto the ω carbon. The oxygen for the group comes from molecular oxygen in a complex reaction that involves cytochrome P450 and the electron donor NADPH. | alcohol dehydrogenase Alcohol dehydrogenase Alcohol dehydrogenases are a group of dehydrogenase enzymes that occur in many organisms and facilitate the interconversion between alcohols and aldehydes or ketones with the reduction of nicotinamide adenine dinucleotide... |
The next step is the oxidation of the hydroxyl group to an aldehyde Aldehyde An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group.... by NAD+. |
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... |
The third step is the oxidation of the aldehyde group to a carboxylic acid Carboxylic acid Carboxylic acids are organic acids characterized by the presence of at least one carboxyl group. The general formula of a carboxylic acid is R-COOH, where R is some monovalent functional group... by NAD+. The product of this step is a fatty acid with a carboxyl group at each end. |
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After the three steps, either end of fatty acid can be attached to coenzyme A
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...
. The molecule can enter the mitochondrion and undergo β oxidation. The final products after successive oxidation include succinic acid
Succinic acid
Succinic acid is a dicarboxylic acid. Succinate plays a biochemical role in the citric acid cycle. The name derives from Latin succinum, meaning amber, from which the acid may be obtained....
, which can enter citric acid cycle
Citric acid cycle
The citric acid cycle — also known as the tricarboxylic acid cycle , the Krebs cycle, or the Szent-Györgyi-Krebs cycle — is a series of chemical reactions which is used by all aerobic living organisms to generate energy through the oxidization of acetate derived from carbohydrates, fats and...
, and adipic acid
Adipic acid
Adipic acid is the organic compound with the formula 42. From the industrial perspective, it is the most important dicarboxylic acid: About 2.5 billion kilograms of this white crystalline powder are produced annually, mainly as a precursor for the production of nylon...
.