The function of the peroxisome

Peroxisomes are organelles that are essential for maintaining cellular function in lipid metabolism, redox homeostasis and intracellular signalling. They are involved in the ß-oxidation of various fatty acids, especially very long chain fatty acids, as well as the synthesis of ether-phospholipids and bile acids in mammals. Substrates for the ß-oxidation are transported into peroxisomes by the ABC transporters ABCD1-3, and the metabolites produced by the ß-oxidation cycle are released from peroxisomes through certain unique transporters and channels on the peroxisomal membrane. The initial steps of ether-phospholipid synthesis take place in peroxisomes, with one of steps being tightly controlled by negative feedback regulation. As peroxisomes have various enzymes that generate reactive oxygen species such as H2O2, their metabolic activity significantly impacts cellular redox balance, which is closely connected to the redox homeostasis in mitochondria. It has been shown that the physical contact sites between peroxisomes and lysosomes, the ER, mitochondria or lipid droplets are formed by tethered proteins and play an important role in the transporting or shuttling of metabolites between peroxisomes and other organelles. Furthermore, peroxisomes tightly collaborate with mitochondria in the antiviral defence system. In this chapter, we describe the current understanding of the peroxisomal metabolic pathways including lipid metabolism and redox metabolism, as well as the crosstalk that takes place between peroxisomes and other organelles.