145. In a metabolic engineering experiment the flux from primary carbon metabolism was diverted
towards methylerythritol phosphate (MEP) pathway. Which one of the following class of secondary
carbon compounds do you think will accumulate more?
A. Alkaloids
B. Glucosinolates
C. Phenolics
D. Terpenes

Redirecting Carbon Flux to the MEP Pathway: A Strategy for Terpene Accumulation

Metabolic engineering often involves rerouting cellular metabolic pathways to increase the production of specific secondary metabolites. One such strategic rerouting is the diversion of flux from primary carbon metabolism toward the methylerythritol phosphate (MEP) pathway, also known as the non-mevalonate pathway.

This pathway plays a central role in the biosynthesis of isoprenoids, a vast and diverse class of secondary metabolites.

What is the MEP Pathway?

The MEP pathway operates primarily in plastids of plant cells and is responsible for producing the isoprenoid precursors:

• Isopentenyl pyrophosphate (IPP)

• Dimethylallyl pyrophosphate (DMAPP)

These precursors serve as the building blocks for a wide range of isoprenoids, including terpenes, which are essential for plant defense, communication, and various industrial applications (e.g., pharmaceuticals, flavors, fragrances).

Which Secondary Metabolite Class Accumulates More?

Correct Answer: D. Terpenes

Redirecting carbon flux to the MEP pathway enhances the production of terpenes, which are isoprenoid-based compounds. Since the MEP pathway directly supplies the precursors for terpene biosynthesis, upregulating this pathway results in higher accumulation of mono-, sesqui-, di-, and triterpenes.

Why Not the Other Options?

• A. Alkaloids: These nitrogen-containing compounds typically derive from amino acid metabolism, not from the MEP pathway.

• B. Glucosinolates: These are sulfur-containing secondary metabolites found mainly in Brassicaceae and are derived from amino acids like methionine.

• C. Phenolics: These arise from the shikimate pathway and phenylpropanoid pathway, unrelated to the MEP pathway.

Conclusion

In metabolic engineering, when the goal is to increase the yield of terpenes, diverting carbon flux toward the MEP pathway is a powerful strategy. This pathway supplies essential isoprenoid intermediates that lead to the accumulation of terpenes, making it highly effective for boosting the production of this important class of secondary metabolites.

Final Answer: D. Terpenes