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Peroxisomes function to rid the body of toxic substances, such as hydrogen peroxide, or other metabolites and contain enzymes concerned with oxygen utilization such as D-amino acid oxidase and urease oxidase . The peroxisome contains the enzyme catalase which converts H₂O₂ (hydrogen peroxide, a toxic byproduct of cellular metabolism) to H₂O and O₂, with 4H₂O₂ → 4H₂O + 2O₂.

High numbers of peroxisomes can be found in the liver, where toxic byproducts are known to accumulate. All of the enzymes found in a peroxisome are imported from the cytosol. Each enzyme transferred to a peroxisome has a special sequence at one end of the protein, called a PTS or peroxisomal targeting signal , that allows the protein to be taken into that organelle, where they then function to rid the cell of toxic substances.

Peroxisomes also degrade fatty acids and toxic compounds and catalyze the first two steps in the synthesis of ether phospholipidA phospholipid is a lipid that is a primary component of cell membranes. Phospholipids consist of a water- soluble head (a positively charged ( polar) group), linked to two water-insoluble nonpolar tails (by a negatively charged phosphate group). Both tais, which are later used to build membranes. Peroxisomes are responsible for oxidation of long-chain fatty acids and thereby generating acetyl groups.

Peroxisomes often resemble a lysosome. However, peroxisomes are self replicating, whereas lysosomes are formed in the Golgi apparatus. Peroxisomes also have membrane proteins that are critical for various functions, such as for importing proteins into their interiors and to proliferate and segregate into daughter cells.

This article or image contains material from the Science Primer published by the NCBI, which, as a US government publication, is in the public domain [1].