Download Oxidation of fatty acids

Oxidation of fatty
acids
Introduction
Central energy yielding pathway in many tissues
As fuel
Chemically inert
Releases lots of energy
Oxidation of fatty acids
Occurs in 3 steps
1. Oxidative removal of successive 2 carbon units in
the form of acetyl CoA.
2. Acetyl groups enter Citric acid cycle to yield CO2
and H2O
3. NADH and FADH2 donate electron to the
mitochondrial chain with ultimate phosphorylation
of ADP to ATP.
Beta - Oxidation
• 4 enzyme catalyzed reactions take place
1) Dehydrogenation of Fatty acyl CoA producing
double bond.
2) Addition of H2O to the double bond to form Lstereoisomer of Beta-Hydroxyacyl CoA.
3) Dehydrogenation to Beta ketoacyl CoA.
4) Thiolysis by thiloase catalyzed reaction to give off 2
C fragment of orig. F.Acid as Acetyl CoA.
TFP or Tri functional protein
• For fatty acyl chain of 12 or more C, the
reactions are catalyzed by a multienzyme
complex associated with the inner
mitochondrial memb., TFP.
Structure of TFP
Heterodimer of Alpha & Beta subnits.
4
4
Alpha has 2 activities
Enoyl CoA hydratase
Beta-Hydroxyacyl-CoA dehydrogenase
4
Beta 4 - Thiolase activity.
Net reaction ( 16 – C palmitic acid )
Beta oxidation
• Palmitoyl CoA + 23O2 +108Pi +108 ADP = CoA +108
ATP + 16CO2 + 23H2O
( The cost of activation of palmitate to palmitoyl CoA
is 2 ATP,
So net gain is 106 ATP)
Beta oxidation of mono-unsat. Fatty
acid
The side diagram shows
the Beta oxid. Of Oleic
Acid.
I. Oleate is an abundant 18-C mono-unsaturated
fatty acid ( cis double bond at C-9 & C-10.
II. Conversion to oleoyl CoA by carnitine shunt
III. 3 passes thr beta oxid. To yield 12 carbon unsat.
Fatty acid as shown in fig
IV. Isomerase enzyme converts cis form to trans
V. Further Beta oxid.
Beta oxidation of poly-unsaturated
fatty acid
If no. of carbons are odd
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