MEVALONATE PATHWAY 

Introduction - 

The mevalonate pathway, also known as the isoprenoid pathway or HMG-CoA reductase pathway, is a metabolic pathway that produces isoprenoids, a large and diverse class of biomolecules.

Stages 

The mevalonate pathway is divided into three stages:

Stage 1: The first step is the condensation of two molecules (acetyl-CoA and acetoacetyl-CoA). 
  • Acetoacetyl-CoA is then converted to 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) by HMG-CoA synthase. 
  • HMG-CoA is then reduced to mevalonate by HMG-CoA reductase.

Stage 2: Mevalonate is phosphorylated twice and decarboxylated to form IPP.

Stage 3: 
  • IPP is condensed with DMAPP to form geranyl pyrophosphate (GPP). 
  • GPP can then be condensed with another IPP to form farnesyl pyrophosphate (FPP), or with two IPPs to form geranylgeranyl pyrophosphate (GGPP). 
  • GPP, FPP, and GGPP are the precursors to a wide variety of isoprenoids, including cholesterol, vitamin K, coenzyme Q10, and steroid hormones.




Significance of Mevalonate Pathway -

  • Cholesterol synthesis: Cholesterol is a major component of cell membranes, and it is also used to synthesize steroid hormones.
  • Protein prenylation: Protein prenylation is a post-translational modification that is essential for the function of many proteins, including small GTPases.
  • Ubiquinone synthesis: Ubiquinone is a component of the electron transport chain, which is responsible for generating ATP.
  • Isoprenoid synthesis: Isoprenoids are a diverse class of biomolecules that play a variety of roles in cells, including signaling, defense, and energy storage.

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