Phosphomevalonic acid

Overview

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Diagram of the mevalonate pathway, showing the role of phosphomevalonic acid.

Phosphomevalonic acid is an important intermediate in the mevalonate pathway, a crucial metabolic pathway that leads to the biosynthesis of isoprenoids and sterols, including cholesterol. This pathway is essential in all higher eukaryotes and many prokaryotes.

Structure and Function

Phosphomevalonic acid, also known as mevalonate-5-phosphate, is a phosphorylated derivative of mevalonic acid. It is formed by the action of the enzyme mevalonate kinase, which catalyzes the phosphorylation of mevalonic acid using ATP as a phosphate donor.

The chemical structure of phosphomevalonic acid includes a six-carbon backbone with a phosphate group attached to the fifth carbon. This modification is critical for its role in the subsequent steps of the mevalonate pathway.

Role in the Mevalonate Pathway

In the mevalonate pathway, phosphomevalonic acid is further phosphorylated by the enzyme phosphomevalonate kinase to form mevalonate-5-diphosphate. This step is crucial for the eventual production of isopentenyl pyrophosphate (IPP), the building block for the synthesis of all isoprenoids.

The pathway proceeds as follows:

1. Mevalonic acid is phosphorylated by mevalonate kinase to form phosphomevalonic acid.
2. Phosphomevalonic acid is then phosphorylated by phosphomevalonate kinase to form mevalonate-5-diphosphate.
3. Mevalonate-5-diphosphate is decarboxylated to form isopentenyl pyrophosphate (IPP).

Biological Significance

The mevalonate pathway, and by extension phosphomevalonic acid, is vital for the production of several key biological molecules. These include:

• Cholesterol, which is a fundamental component of cell membranes and a precursor for steroid hormones.
• Ubiquinone (coenzyme Q), which is essential for the electron transport chain in mitochondria.
• Dolichol, which is involved in the glycosylation of proteins.

Clinical Relevance

Disruptions in the mevalonate pathway can lead to various metabolic disorders. For example, deficiencies in mevalonate kinase can result in mevalonate kinase deficiency, a rare genetic disorder that can cause developmental delays and immune system dysfunction.

Additionally, the mevalonate pathway is the target of statins, a class of drugs used to lower cholesterol levels in patients with hypercholesterolemia. Statins inhibit HMG-CoA reductase, the enzyme that catalyzes the rate-limiting step of the pathway.

Related Pages

• Mevalonate pathway
• Cholesterol
• Isoprenoids
• Statins