Mevalonate pathway

Definition

The mevalonate pathway is a metabolic pathway used by organisms to synthesize isoprenoids, including cholesterol and many plant secondary metabolites. This pathway plays a crucial role in producing key compounds that are essential for various biological functions, including growth, reproduction, and defense mechanisms in plants.

5 Must Know Facts For Your Next Test

1. The mevalonate pathway begins with the condensation of acetyl-CoA to form acetoacetyl-CoA, eventually leading to the production of mevalonate and isoprenoid precursors.
2. It is particularly significant in plants as it facilitates the biosynthesis of secondary metabolites such as terpenes and alkaloids, which play critical roles in plant defense against herbivores and pathogens.
3. The pathway occurs in the cytosol of plant cells, distinguishing it from the alternative methylerythritol phosphate (MEP) pathway found in plastids.
4. Enzymes like HMG-CoA reductase are key regulatory points in this pathway and are often targets for herbicides or inhibitors due to their role in controlling isoprenoid production.
5. The end products of the mevalonate pathway include not only terpenes but also important molecules like steroid hormones and vitamins, underscoring its biological importance.

Review Questions

• How does the mevalonate pathway contribute to plant defense mechanisms?
  • The mevalonate pathway is essential for synthesizing various secondary metabolites that aid in plant defense. Compounds such as terpenes and alkaloids produced through this pathway deter herbivores and protect against pathogens. These metabolites act as chemical defenses or attract predators of herbivores, thereby enhancing the plant's overall survival and fitness.
• Discuss the significance of HMG-CoA reductase in the mevalonate pathway and its implications for agricultural practices.
  • HMG-CoA reductase serves as a major regulatory enzyme in the mevalonate pathway, controlling the flow of substrates toward isoprenoid biosynthesis. Its importance lies in the fact that inhibiting this enzyme can lead to reduced production of vital secondary metabolites. This makes HMG-CoA reductase a target for herbicides, as altering its activity can help manage plant growth or stress responses, which can be strategically used in agricultural practices.
• Evaluate the role of the mevalonate pathway in synthesizing secondary metabolites compared to the MEP pathway and how this reflects on plant adaptability.
  • The mevalonate pathway plays a unique role in synthesizing secondary metabolites primarily in the cytosol, while the MEP pathway operates within plastids. Both pathways contribute significantly to producing isoprenoids but respond differently to environmental stimuli. By having two distinct pathways, plants can adapt to varying conditions by modulating their metabolite production based on environmental challenges, providing them with flexibility to enhance survival through diverse chemical defenses.

Related terms

Isoprenoids: A diverse class of organic compounds derived from five-carbon isoprene units, playing significant roles in cellular signaling, growth, and photosynthesis.

Cholesterol: A type of lipid molecule that is a vital component of cell membranes and serves as a precursor for the synthesis of steroid hormones and bile acids.

Terpenes: Organic compounds formed from the polymerization of isoprene units, known for their roles in plant defense and aromatic properties.