A mutation in CPT2 resulted in infantile death. This mutation was also expressed

Question

A mutation in CPT2 resulted in infantile death. This mutation was also expressed in COS-l cells at the same level as WT-CPT2, but resulted in only a 2% increase in fatty acid oxidation. The next day, the experiment was repeated, but about a 20% increase in fatty acid oxidation was observed. The person performing these experiments went back and checked his solutions and found that he had accidently added 10X as much carnitine to these cells in the second experiment. He was able to reproduce both results by varying the amount of carnitine that was added. Increasing the carnitine concentration to 100X the original concentration resulted in an 80% increase in fatty acid oxidation. What kinetic parameter for the CPT2 reaction is affected by this mutation?

Explanation / Answer

The parameter that is altered is the Km of the enzyme. It is the substrate concentration at which an enzyme attains half its maximum activity. A very high substrate concentration requirement to achieve maximum activity indicates that the enzyme has high Km.It further describes that the mutation decreased the affinity of the enzyme to the substrate, and hence, a high concentration of substrate is required for its maximum activity.

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