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 Oxidative removal of successive 2 carbon units in the form of acetyl CoA. Acetyl groups enter Citric acid cycle to yield CO2 and H2O NADH and FADH2 donate electron to the mitochondrial chain with ultimate phosphorylation of ADP to ATP.

Beta - Oxidation 4 enzyme catalyzed reactions take place Dehydrogenation of Fatty acyl CoA producing double bond. Addition of H2O to the double bond to form L- stereoisomer of Beta-Hydroxyacyl CoA. Dehydrogenation to Beta ketoacyl CoA. 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 Alpha4 & Beta4 subnits. Alpha4 has 2 activities Enoyl CoA hydratase Beta-Hydroxyacyl-CoA dehydrogenase 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.

Oleate is an abundant 18-C mono-unsaturated fatty acid ( cis double bond at C-9 & C-10. Conversion to oleoyl CoA by carnitine shunt 3 passes thr beta oxid. To yield 12 carbon unsat. Fatty acid as shown in fig Isomerase enzyme converts cis form to trans Further Beta oxid.

Beta oxidation of poly-unsaturated fatty acid

If no. of carbons are odd

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