Biochemistry

1. BETA OXIDATION OF
FATTY ACIDS
PRATEEK KUMAR GAUTAM
105

2. • Fats are important source of energy as(1gm of
fat gives 9kcal energy)
• Fats constitute 84% of stored energy
protiens-15%
carbohydrates- < 1%
Sources:-
Diet-short and medium chain fatty acids.
Chylomicrons and VLDL.
TAG-From adipose tissue.

3. BETA OXIDATION OF FATTY ACIDS
• Definition-The oxidation of hydrocarbon chain
by sequential cleavage from beta carbon to
form acetyl CoA.
• Site- Mitochondria of almost all the cells
including liver ,kidney, heart.
• It is an aerobic process.

4. Stages of beta oxidation
3 stages :-
1) Activation of fatty acids.
2) Transport of activated fatty acid from cytosol
to mitochondria.
3)Beta oxidation proper.

5. Activation of fatty acid
• It is the conversion of fatty acid to its
coenzyme.
Fatty acid Acyl CoA
• Enzyme- Thiokinase or Acyl CoA synthatase.
• Requirements- ATP , coenzyme A ,
Magnesium ion.
• This reaction is totally irreversible.

7. Transport of fatty acid
• Short chain and medium chain fatty acids can
pass through the mitochondrial membrane.
• But long chain fatty acid cannot pass through
the mitochondrial membrane. So a
transporter carnitine is involved in its transfer.
• So this process is also known as carnitine
shuttle system.
• Enzyme- Carnitine acyl transferase.
• Transporter protein- Translocase.

9. Beta oxidation proper
• It undergoes sequence of four reaction
leberating two carbon unit acetyl CoA.
1. FAD+ dependent oxidation.
2. Hydration.
3. NAD+ dependent oxidation.
4. Cleavage.

10. Step 1- Oxidation
• Acyl CoA undergoes dehydrogenation.
• Enzyme- Acyl CoA dehydrogenase
• Co enzyme- FAD

11. Step 2- Hydration
• Enzyme- Enoyl CoA hydratase

12. Step 3- oxidation
• Enzyme - Beta hydroxy acyl dehydrogenase
• Coenzyme – NAD+

13. Step 4- Cleavage
• Beta keto fatty acid undergoes thiolytic
cleavage, splitting off a molecule of acetyl
CoA.
• Enzyme – Thiolase.

14. Further reactions
• Newly formed acetyl CoA will further
participate in TCA cycle for complete oxidation
into CO2 and water.
• Remaining fatty acyl CoA will repeat step
1,2,3,4 of beta oxidation until it is completely
converted into acetyl CoA.

17. Energetics
• 8 acetyl-CoA = 80 ATP
• 7 FADH2 x 1.5 = 10.5 ATP
• 7 NADH x 2.5 = 17.5 ATP
• Gross total = 108 ATP
• Net yield = 108 -2 =106 ATP

18. Regulation of beta oxidation
1. Availability of free fatty acid.
2. Glucagon : Insulin.
3. During denovo synthesis of fatty acid beta
oxidation of fatty acid is inhibited as malonyl
CoA inhibits the action of CAT1

19. THANK YOU