Beta oxidation of fatty acid

Lipid metabolism i.e. beta oxidation of fatty acid

1. School of Applied Science, CUTM, BBSR

2. CONTENTS
Fatty acid oxidation
Types of fatty acid oxidation
Overview of fatty acid oxidation
Beta-Oxidation of fatty acid
Steps in Beta-Oxidation of fatty acid
Stoichiometryof Beta oxidation
Reference

3. Fatty acid oxidation
Fattyacidcontainsalonghydrocarbonchainandaterminalcarboxylategroup.
Thehydrocarbonchainmaybesaturated(withnodoublebond)ormaybe
unsaturated(containingdoublebond).
FattyacidOxidationistheprocesswhereenergyisproducedbydegradationof
fattyacids.
•Major mechanism, occurs in themitochondriamatrix.
•2-C units are released asacetylCoAper cycle
Beta oxidation
•Predominantly takes place inbrainand liver,
•one carbon is lost in the form ofCO2 per cycle
Alpha
oxidation
•Minor mechanism, but becomes important in
conditions of impaired beta oxidation
Omega
oxidation
Types of fatty acid oxidation

4. Stage1:
Along-chainfattyacidis
oxidizedtoyieldacetyl
residuesintheformofacetyl-
CoA.Thisprocessiscalled
Betaoxidation.
Stage 2:
Theacetylgroupsare
oxidizedtoCO2viathe
citricacidcycle.
Stage3:
Electronsderivedfromtheoxidations
ofstages1and2passtoO2viathe
mitochondrialrespiratorychain,
providingtheenergyforATPsynthesis
byoxidativephosphorylation.
Overview of fatty acid oxidation

5. Beta-Oxidationmaybedefinedastheoxidationoffattyacidsonthebeta-
carbonatom.
Thisresultsinthesequentialremovalofatwocarbonfragment,acetylCoA.
Occursinthemitochondriaandstrictlyaerobic.
AfterproductionAcetyl-CoAisfeddirectlyintotheKrebscycle.
Itoccursinmanytissuesincludingliver,kidneyandheart.
Fattyacidsoxidationdoesn'toccurinthebrain.
Beta-Oxidation of fatty acid
Steps in Beta-Oxidation of fatty acid

6. Steps -1; Activation of fatty acid

7. The inner mitochondrial membrane is impermeable to fatty acids.
A specialized carnitinecarrier system (carnitineshuttle) operates to transport
activated fatty acids from cytosolto the mitochondria.
This occurs in four steps
1.Acylgroup of acylCoAis transferred to carnitine(β-hydroxyγ-trimethyl
aminobutyrate) catalyzed by carnitineacyltransferasIe(CAT) (present on the outer
surface of inner mitochondrial membrane).
2.The acyl-carnitineis transported across the membrane to mitochondrial matrix by a
specific carrier protein.
3.Carnitineacyltransferasell(found on the inner surface of inner mitochondrial
membrane) converts acyl-carnitineto acylCoA.
4.The carnitinereleased returns to cytosolfor reuse.
Steps -2; Transport of fatty acid into mitochondria

8. Eachcycleofβ-oxidation,liberatingatwocarbonunit-acetylCoA,occursina
sequenceoffourreactions
1.Oxidation
2.Hydration
3.Oxidation
4.Cleavage.
1.Oxidation
•AcylCoAundergoesdehydrogenationbyanFAD-dependentflavoenzyme,acyl
CoAdehydrogenase.
•Adoublebondisformedbetweenαandβcarbons(i.e.,2and3carbons)
Steps -3; Beta-Oxidation proper

9. 2.Hydration:
•EnoylCoAhydratasebringsaboutthehydrationofthedoublebondtoformβ-
hydroxyacylCoA.
3.Oxidation
•β-HydroxyacylCoAdehydrogenasecatalysesthesecondoxidationand
generatesNADH.
•Theproductformedisβ-ketoacylCoA.

10. 4.Cleavage
•Thefinalreactioninβ-oxidationistheliberationofa2carbonfragment,acetyl
CoAfromacylCoA.
•Thisoccursbyathiolyticcleavagecatalysedbyβ-ketoacylCoAthiolase(or
thiolase).
ThenewacylCoA,containingtwocarbonslessthantheoriginal,reenterstheβ-
oxidationcycle.
Theprocesscontinuestillthefattyacidiscompletelyoxidized.

11. Stoichiometryof Beta oxidation

12. Reference
Cox, Michael M., and David L. Nelson.Lehningerprinciples of
biochemistry. Vol. 5. New York: WhFreeman, 2008.
Pranav, K., & Mina, U. (2013).Life Sciences: Fundamentals and
practice. New Delhi: Pathfinder Academy.
Satyanarayana, U. (2014).Metabolism of lipids.