Alpha oxidation
Oxford Dictionary of Biochemistry:
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alpha oxidation
or α-oxidation
- a series of reactions occurring in plant tissue by which a free fatty acid of chain length ranging from C18 to C13 is oxidatively degraded with the simultaneous release of a molecule of CO2 from the carboxyl group and the formation of a free fatty acid containing one carbon atom fewer. NAD+ is the only cofactor required.
- In animals, the first reaction in the oxidation of phytanic acid in peroxisomes. It is catalysed by phytanoyl-CoA hydroxylase, deficiency of which produces Refsum disease (classical or adult).
| alpha hemolysis, alpha helix, alpha globulin | |
| alpha particle, alpha radiation, alpha ray |
Wikipedia on Answers.com:
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Alpha oxidation
Alpha oxidation (α-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, which cannot undergo beta-oxidation due to its β-methyl branch, into pristanic acid, which can.
Pathway
Alpha-oxidation of phytanic acid is believed to take place entirely within peroxisomes.
- Phytanic acid is first attached to CoA to form phytanoyl-CoA.
- Phytanoyl-CoA is oxidized by phytanoyl-CoA dioxygenase, in a process using Fe2+ and O2, to yield 2-hydroxyphytanoyl-CoA.
- 2-hydroxyphytanoyl-CoA is cleaved by 2-hydroxyphytanoyl-CoA lyase in a TPP-dependent reaction to form pristanal and formyl-CoA (in turn later broken down into formate and eventually CO2).
- Pristanal is oxidized by aldehyde dehydrogenase to form pristanic acid (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) leads to Refsum's disease, in which the accumulation of phytanic acid and its derivatives leads to neurological damage. Other disorders of peroxisome biogenesis also prevent alpha-oxidation from occurring.
References
- Casteels, M; Foulon, V; Mannaerts, GP; Van Veldhoven, PP (2003), "Alpha-oxidation of 3-methyl-substituted fatty acids and its thiamine dependence", European journal of biochemistry / FEBS 270 (8): 1619–1627, doi:10.1046/j.1432-1033.2003.03534.x, PMID 12694175
- Quant, Patti A.; Eaton, Simon, eds. (1999), Current views of fatty acid oxidation and ketogenesis : from organelles to point mutations, 466 (2nd ed.), New York, NY: Kluwer Acad./Plenum Publ., pp. 292–295, ISBN 0-306-46200-1
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Oxford Dictionary of Biochemistry
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