This document summarizes fatty acid oxidation and beta-oxidation. It describes that fatty acid oxidation occurs in the mitochondria to break down fatty acids into acetyl-CoA, generating energy. Beta-oxidation involves four steps - oxidation, hydration, oxidation again, and cleavage - to sequentially remove two-carbon acetyl-CoA units from the fatty acid. The acetyl-CoA can then enter the citric acid cycle to generate more energy through oxidative phosphorylation.

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
Stoichiometry of Beta oxidation
Reference

3. Fatty acid oxidation
Fatty acid contains a long hydrocarbon chain anda terminal carboxylate group.
 The hydrocarbonchain may be saturated (with no double bond) or may be
unsaturated (containing double bond).
 Fatty acid Oxidation is the process where energy is produced by degradation of
fatty acids.
• Major mechanism, occurs in themitochondria matrix.
• 2-C units are released asacetyl CoA per cycle
Beta oxidation
• Predominantly takes place inbrain and 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. Stage 1:
A long-chain fatty acid is
oxidized to yield acetyl
residues in the form of acetyl-
CoA. This process is called
Beta oxidation.
Stage 2:
The acetyl groups are
oxidized to CO2 via the
citric acid cycle.
Stage 3:
Electrons derived from the oxidations
of stages 1 and 2 pass to O2 via the
mitochondrial respiratory chain,
providing the energy for ATP synthesis
by oxidative phosphorylation.
Overview of fatty acid oxidation

5.  Beta-Oxidation may be defined as the oxidation of fatty acids on the beta-
carbon atom.
 This results in the sequential removal of a two carbon fragment, acetyl CoA.
 Occurs in the mitochondria and strictly aerobic.
After production Acetyl-CoA is fed directly into the Krebs cycle.
 It occurs in many tissues including liver, kidney and heart.
 Fatty acids oxidation doesn't occur in the brain.
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 carnitine carrier system (carnitine shuttle) operates to transport
activated fatty acids from cytosol to the mitochondria.
 This occurs in four steps
1. Acyl group of acyl CoA is transferred to carnitine (β-hydroxy γ-trimethyl
aminobutyrate) catalyzed by carnitine acyltransferasIe (CAT) (present on the outer
surface of inner mitochondrial membrane).
2. The acyl-carnitine is transported across the membrane to mitochondrial matrix by a
specific carrier protein.
3. Carnitine acyl transferase ll (found on the inner surface of inner mitochondrial
membrane) converts acyl-carnitine to acyl CoA.
4. The carnitine released returns to cytosol for reuse.
Steps -2; Transport of fatty acid into mitochondria

8.  Each cycle of β -oxidation, liberating a two carbon unit-acetyl CoA, occurs in a
sequence of four reactions
1. Oxidation
2. Hydration
3. Oxidation
4. Cleavage.
1. Oxidation
• Acyl CoA undergoes dehydrogenation by an FAD-dependent flavoenzyme, acyl
CoA dehydrogenase.
• A double bond is formed between α and β carbons (i.e., 2 and 3 carbons)
Steps -3; Beta-Oxidation proper

9. 2.Hydration:
• Enoyl CoA hydratase brings about the hydration of the double bond to form β -
hydroxyacyl CoA.
3.Oxidation
• β-Hydroxyacyl CoA dehydrogenase catalyses the second oxidation and
generates NADH.
• The product formed is β-ketoacyl CoA.

10. 4.Cleavage
• The final reaction in β -oxidation is the liberation of a 2 carbon fragment, acetyl
CoA from acyl CoA.
• This occurs by a thiolytic cleavage catalysed by β-ketoacyl CoA thiolase (or
thiolase).
 The new acyl CoA, containing two carbons less than the original, reenters the β-
oxidation cycle.
 The process continues till the fatty acid is completely oxidized.

11. Stoichiometry of Beta oxidation

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