Peroxisomes

Peroxisome Structure and Formation

• Diameter of peroxisomes is approximately 0.1 to 1.0 micrometers.
• Integral membrane proteins of peroxisomes are synthesized in the endoplasmic reticulum.
• Peroxisomes replicate by a process known as "fission."
• Peroxisomal precursor vesicles are formed in the endoplasmic reticulum.

Protein Synthesis and Composition

• Most peroxisome matrix and membrane proteins are synthesized in the cytosol.
• There are at least 32 known peroxisomal proteins, called peroxins, that participate in peroxisome assembly.

Lifespan and Degradation

• The approximate half-life of peroxisomes is 20 days.
• Peroxisomes are degraded through a process called autophagy, specifically via selective autophagy.

Functions and Processes

• Primary function of peroxisomes includes the breakdown of fatty acids and detoxification of harmful substances.
• Peroxisomes convert fatty acids into acetyl CoA through β-oxidation.
• Synthesis of bile acids primarily occurs in the liver.
• Lipid molecules synthesized in peroxisomes include plasmalogens and ether lipids.

Enzymatic Processes

• Catalase enzyme is responsible for the conversion of excessive hydrogen peroxide (H2O2) into water and oxygen.
• Reactive oxygen species detoxified in peroxisomes include hydrogen peroxide and superoxide anions.
• Primary role of catalases in peroxisomes is to eliminate hydrogen peroxide, preventing oxidative damage.

Additional Information

• The product of the oxidation of ethanol in peroxisomes is acetaldehyde, which can then be further oxidized.
• Peroxisomes are also involved in the synthesis of plasmalogens, which play an important role in membrane integrity and function.
• Processes NOT associated with peroxisomes typically include protein synthesis, which occurs predominantly in ribosomes.