Cell Biology/Peroxisomes

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It used to be thought that peroxisomes are formed by the budding of smooth Endoplasmic Reticulum (ER). However, now it is thought that they form through self-assembly. (I will get more information references as I do some more thorough literature searches). The peroxisome is another major source of Oxygen utilization (along with the mitochondrion). There are specific proteins associated with the peroxisomes membrane, also there are 3 oxidation enzymes associated with peroxisomes:


 * 1) D-amino acid oxidase
 * 2) Urate Oxidase
 * 3) Catalase

The enzyme contents vary with various types of cells. One of the main functions of peroxisomes in liver cells is detoxification. This is done by the oxidation of substances like:


 * 1) Alcohol - About 1/2 of the ethanol one drinks is converted to acetaldehyde by oxidation.
 * 2) Phenols
 * 3) Formic acid
 * 4) Formaldehyde

Why peroxisomes are not like lysosomes
Peroxisomes are organelles that contain oxidative enzymes, such as D-amino acid oxidase, urate oxidase, and catalase. They may resemble a lysosome, however, they are not formed in the Golgi complex. Peroxisomes are distinguished by a crystalline structure inside a sac which also contains amorphous gray material. They are self replicating, like the mitochondria. Components accumulate at a given site and they can be assembled into a peroxisome. They may look like storage granules, however, they are not formed in the same way as storage granules.

Peroxisomes function to rid the body of toxic substances like hydrogen peroxide, or other metabolites. They are a major site of oxygen utilization and are numerous in the liver where toxic byproducts are going to accumulate.

The peroxisome is made as a phospholipid bilayer, encapsulating oxidative materials. They would be 'sphere-ish' in shape, not necessarily a perfect sphere, and sometimes, they may take other shapes. But most electron micrographs I have seen (2 dimensions) show them as circles. (As you may be aware, the Cell membrane is also a phospholipid bilayer.) Peroxisomes have membrane proteins that are critical for peroxisomal function, to import proteins into their interiors, proliferate or segregate to daughter cells (This update, thanks to Babich Temps). The main differences would be:


 * 1) Types of phospholipids used.
 * 2) Size of the membrane (i.e. peroxisomes are MUCH smaller than the cell).

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