Peroxisomes Definition

• A range of metabolic processes including various elements of energy metabolism use oxidative enzymes found in peroxisomes, which are tiny, membrane-enclosed cellular organelles.
• These are regarded as a significant subset of microbodies that are present in both plant and animal cells.
• After having already been characterized, they were recognized as organelles by Belgian cytologist Christian de Duve in 1967.
•  The very first peroxisomes were found in Spinach leaf homogenate.
• The cells of detoxifying organs like the liver and kidneys contain them in the greatest amounts. They however, may be made to multiply in response to metabolic requirements.

Structure of Peroxisomes

• These are membrane-bound spherical entities with diameters ranging from 0.2 to 1.5 μm that are present in all eukaryotic cells, including those of both plants and animals.
• They are discovered in close proximity to the ER, mitochondria, or chloroplast in the cell, floating freely in the cytoplasm.
• They are some of the most straightforward eukaryotic organelles.
• They can be found as isolated microperoxisomes or as part of the peroxisome reticulum, a system of linked tubules.
• Depending on the cell, they can vary in size and form, but often have circular cross-sections.
• Their diameter ranges from 0.2 to 1.5 μm.
• It comprises a single lipid-and protein-based limiting membrane that encloses the granular matrix.
• Fibrils, or a crystalloid structure containing enzymes make up the matrix.

Peroxisomal Enzymes

• The matrix of peroxisomes contains over 60 recognized enzymes.
• They are in-charge of performing the oxidation processes that result in the creation of hydrogen peroxide.
• The principal categories of enzymes are:

1. Urate oxidase
2. D-amino acid oxidase
3. Catalase

Functions of Peroxisomes

1. Hydrogen Peroxide Metabolism:

The peroxisomes’ enzymes are involved in the synthesis and removal of the reactive oxygen species H202.

2. Fatty acid oxidation:

In animal cells, fatty acid oxidation takes place in both peroxisomes and mitochondria, but solely in peroxisomes in yeast and plants.

H202 is produced as a by-product of oxidation and is broken down by the catalase enzyme. A significant supply of metabolic energy is offered by this.

3. Lipid biosynthesis

Both ER and peroxisomes are involved in the synthesis of cholesterol and dolichol. In the liver, cholesterol is converted into bile acid.

Enzymes for the synthesis of plasmalogens, a family of phospholipids that are crucial membrane constituents of heart and brain tissue, are found in peroxisomes.

4. Germination of seeds

Peroxisomes in seeds convert fatty acids that have been stored there into carbohydrates, which is essential for giving germination plants the energy and resources they need to grow.

5. Photorespiration

Together with chloroplasts, peroxisomes in leaves, especially green ones, perform the photorespiration process.

6. Degradation of purines

Purine, polyamine, and amino acid catabolism should be carried out, in particular by uric acid oxidase.

7. Bioluminescence

Firefly peroxisomes contain the luciferase enzyme, which promotes bioluminescence and helps the flies find a mate or food.

References

• Verma, P. S., & Agrawal, V. K. (2006). Cell Biology, Genetics, Molecular Biology, Evolution & Ecology (1 ed.). S .Chand and company Ltd.
• Alberts, B. (2004). Essential cell biology. New York, NY: Garland Science Pub.
• Kar,D.K. and halder,S. (2015). Cell biology genetics and molecular biology.kolkata, New central book agency
• R and suwal,S.N. (2010).Human Anatomy and physiology. Kathmandu, vidyarthi prakashan (p.) ltd.
• https://micro.magnet.fsu.edu/cells/peroxisomes/peroxisomes.html
• https://www.britannica.com/science/peroxisome
• http://www.biologydiscussion.com/cell/difference-and-similarity-between-lysosomes-and-peroxisomes-biology/1834
• http://study.com/academy/lesson/peroxisomes-definition-structurefunctions.html#courseInfo