4) (1 pt) An experimenter studying the oxidation of fatty acids in extracts of l

Question

4) (1 pt) An experimenter studying the oxidation of fatty acids in extracts of liver found that when palmitate (16:0) was provided as substrate, it was completely oxidized to CO2. (Acetyl CoA is oxidized through the citric acid cycle). However, when undecanoic acid (11:0) was added as substrate, incomplete oxidation occurred unless he bubbled CO2 through the reaction mixture. The addition of the protein avidin, which binds tightly to biotin, prevented the complete oxidation of undecanoic acid even in the presence of CO2, although it had no effect on palmitate oxidation.

Explain these observations in light of what you know of fatty acid oxidation reactions.

a) What will be the products of undecanoic acid metabolism in the absence of biotin? (after ?-oxidation)

b) What kind of enzyme do you think is required for the complete oxidation of undecanoic acid? And why you think it is this type of enzyme? (if no explanation in your answer no credit)

Explanation / Answer

Oxidation of odd-chain fatty acid yields acetyl-CoA + propionyl-CoA.

The reaction CO2 + propionyl-CoA ? methylmalonyl-CoA that is catalyzed by propionyl-CoA carboxylase, and that is a biotin-containing enzyme, which is therefore inhibited by avidin.

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