The role of peroxisomes in mammalian cellular metabolism.

Peroxisomes, which are widely distributed in mammalian tissues, carry out several important functions in cellular metabolism. Production of alkylglycerol-3-phosphate, a key intermediate in the synthesis of plasmalogens and other ether lipids, occurs in the peroxisome. A fatty acid beta-oxidation system with significant differences from mitochondrial beta-oxidation is also found in the peroxisomes; the acetyl-CoA produced is used for synthetic reactions. This pathway has a particularly important physiological role in the oxidation of very long chain fatty acids and the side chain of cholesterol. Peroxisomes also possess a number of oxidases that produce H2O2 which is decomposed by peroxisomal catalase. The function of this peroxisomal respiratory pathway is disposal of excess reducing equivalents, protection of the cell against H2O2 and possibly a role in thermogenesis in brown adipose tissue. Other peroxisomal functions include a role in gluconeogenesis and in purine and polyamine catabolism. Some enzymes of peroxisomes can be induced by dietary, hormonal and other physiological changes. The entire organelle proliferates under certain of these conditions.