The Structure and Function of Peroxisomes

Edited by Jen Moreau, Marisha

Peroxisomes are cytoplasmic organelles. De-Duve and coworkers isolated peroxisomes from liver cells and some other tissues. They are present in both animal and plant cells. They are also found in protozoa, yeast and many types of cells in higher plants.

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Structure:

Structure: 43844.jpg

Peroxisomes are enclosed in a single membrane. Their size is 0.5 micrometer in diameter. In some mammalian tissues, peroxisomes form an extensive network. They contain more than 50 enzymes. Peroxisomes self-replicate by enlarging and then dividing. They contain H2O2 producing enzymes like oxidases and catalases. They also contain some oxidative enzymes like peroxidase, Catalase, glycolic acid oxidase and some other enzymes. Proteins are selectively imported into peroxidases. Peroxisomes contain no DNA or ribosomes. Therefore, they have no means of producing proteins. Thus, all of these proteins are imported across the membranes.

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Functions:

Functions: 90637.jpg

  • Peroxisomes are involved in the formation and decomposition of Hydrogen peroxide. The word peroxisome is derived from hydrogen peroxide. Peroxisome contains oxidative enzymes, such as catalase, D-amino acid oxidase and uric acid oxidase. They use molecular oxygen to remove hydrogen atoms from a specific organic substrate (R) in an oxidative reaction. It produces Hydrogen peroxide (H2O2 is a toxic byproduct of cellular metabolism).
                   RH2 + O2                                 R+ H2O2
  • Catalases uses this H2O2 in the peroxisome to oxidize other substrates like phenols, formic acid, formaldehyde, and alcohol:
                   H2O2 + R'H2                            R' + 2H2O

This reaction is important in liver and kidney cells where the peroxisomes detoxify various toxic substances that enter the blood. In addition, when excess H2O2 accumulates in the cell, catalase converts it to H20 through this reaction:

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                   2H2O2 	                             2H2O + O2
  • Peroxisomes are important for lipids metabolism. In humans, Oxidation of fatty acids greater than 18 carbons in length occurs in peroxisomes. In yeast, all fatty acid oxidation occurs in peroxisomes. A major function of peroxisomes is the breakdown of fatty acid molecules in a process called beta-oxidation. In this process, the fatty acids are broken down into Acetyl-CoA. It is then transported to back to the cytosol for further use.

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  • Peroxisomes contain the first two enzymes required for the synthesis of plasmalogens (myelin sheath).
  • Peroxisomes also play important roles in cholesterol and bile acid synthesis, purine and polyamine catabolism, and prostaglandin metabolism.
  • In plants, peroxisomes are required for photorespiration.

Deficiency:

A deficiency in the protein in peroxisomes causes abnormalities in the brain called Zellweger syndrome. A deficiency in the Peroxin Pex 2 is responsible another form of the syndrome.

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The Structure and Function of Peroxisomes. (2017). In ScienceAid. Retrieved Mar 25, 2017, from https://scienceaid.net/the_Structure_and_Function_of_Peroxisomes

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MLA (Modern Language Association) "The Structure and Function of Peroxisomes." ScienceAid, scienceaid.net/the_Structure_and_Function_of_Peroxisomes Accessed 25 Mar 2017.

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Categories : Molecular Biology

Recent edits by: Jen Moreau

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