Peroxiredoxin

Overview

Structure of Peroxiredoxin

Peroxiredoxins are a family of antioxidant enzymes that play a crucial role in reducing peroxides, such as hydrogen peroxide and organic hydroperoxides, to water and alcohols, respectively. They are found in a wide range of organisms, from bacteria to humans, and are involved in protecting cells from oxidative damage.

Structure

Peroxiredoxins are characterized by their cysteine-based catalytic mechanism. The active site of peroxiredoxins contains a conserved cysteine residue, known as the peroxidatic cysteine, which is essential for their enzymatic activity. Upon reaction with a peroxide substrate, this cysteine is oxidized to a sulfenic acid intermediate.

Mechanism of Action

Peroxiredoxins function through a catalytic cycle that involves the reduction of peroxides. The peroxidatic cysteine is oxidized to cysteine sulfenic acid, which is then reduced back to cysteine by a thiol-containing reducing agent, such as thioredoxin. This cycle allows peroxiredoxins to continuously detoxify peroxides in the cell.

Types of Peroxiredoxins

There are several types of peroxiredoxins, classified based on their structure and the number of cysteine residues involved in the catalytic cycle:

• 1-Cys Peroxiredoxins: These have only one conserved cysteine residue involved in the catalytic cycle.
• 2-Cys Peroxiredoxins: These have two conserved cysteine residues, forming an intermolecular disulfide bond during the catalytic cycle.
• Atypical 2-Cys Peroxiredoxins: These have two cysteine residues but form an intramolecular disulfide bond.

Biological Functions

Peroxiredoxins are involved in various cellular processes, including:

• Antioxidant Defense: They protect cells from oxidative stress by reducing peroxides.
• Signal Transduction: They participate in redox signaling by modulating the activity of other proteins through reversible oxidation.
• Cell Proliferation and Differentiation: They are involved in regulating cell growth and differentiation.

Clinical Significance

Alterations in peroxiredoxin expression and function have been associated with various diseases, including cancer, neurodegenerative disorders, and cardiovascular diseases. Their role in maintaining redox balance makes them potential targets for therapeutic intervention.

Related Pages

• Antioxidant
• Enzyme
• Oxidative stress
• Thioredoxin