Peroxisomes get their name from the hydrogen peroxide produced as a by-product of the activites of oxidative nezymes. Hydrogen peroxide is dangerous to cells becasue of its violent chemical reactivity. However, peroxisomes also contain the enzyme catalase, which ctalyzes the decomposition of hydrogen peroxide into water and oxgen.
Unlike mitochondria, peroxisomes do not contain DNA or ribosomes. Thus all of their proteins must be imported from the cytosol. As with mitochondria and the ER, new perosisomes arise from fission from preexisting peroxisomes.
Peroxisomes can form from the fusion of ER dervied visciles. These vesicles then import peroxisomal proteins to form a mature peroxisome.
Function of Peroxisomes:
Peroxisomes are microbodies that contain enzymes used to oxidze fatty acids. If these oxidative enzymes were free in the cytoplasm, they could short circuti cellular metabolism, which often involves adding hydrogen atoms to oxygen.
Peroxisomes catalyze the first reactions in the formation of plasmalogens which are the most abundant class of phosphlipids in myelin. Deficiency of plasmalogens causes profound abnormalities in the myleination of nerve cells. In addition to an ethanolamine head group, plasmalogens contain a glycerol phosphate backbone which is attached to a fatty acid which contains an ether linkage.
Peroxisomes also contain enzyme(s) that use molecular oxygen to remove hydrogen atoms in an oxidative reaction that produces hydrogen peroxide (H2O2) which is then used in the liver and kidney cells to oxidize other substrates to detoxify other molecules.
Peroxisome Signal Sequences:
SKL Sequence: A specific sequence, SKL (serine, lysine, leucine) at the C terminus of many peroxisomal proteins serves as an import signal to peroxisomes.
Peroxins: There are soluble receptor proteins called peroxins. A peroxin pex receptor for example accompanies its cargo all the way into peroxisomes much like protein transport into the nucleus. Thus the protein folds as it is transported just as with nuclear transport and ATP is required.
Genetic Diseaes related to Peroxisomes:
Some 32 genes thta econde prtoeins involved in biogenesis and maintenace of peroxisomes.
Peroxisome biogenesis disorders (PBMDs) can be caused by mutation in some of the genes known to be involved in biogenesis and maintenance of peroxisomes.