Morphogenesis of Peroxisomes in Lipid-Synthesizing Epithelia

Abstract

The discovery of a fatty acyl-CoA oxidizing system in rat liver peroxisomes (1) provided convincing evidence that peroxisomes are engaged in lipid metabolism. Furthermore, during the last decade it has been clearly established that more than half of the known proteins of rat liver peroxisomes are lipid-metabolizing enzymes, involved in catabolic as well as in anabolic pathways. Thus, the biochemical findings corroborate early morphological observations pointing to the functional implication of peroxisomes in lipid metabolism and underline the significance of morphological parameters, such as the close spatial relationship between peroxisomes and lipid droplets, the abundance of tubular organelles (50 – 100 nm in diameter — “microperoxisomes”) in lipid-secreting cells or the proliferation of peroxisomes, e.g. induced by hypolipidemic drugs (2 – 4). Unlike most internal tissues, sebaceous glands accumulate unique lipids of extraordinary complexity, such as ether lipids, wax esters, and sterol esters, as well as various unusual intermediates of the cholesterol pathway, e.g. squalene, farnesol or lanosterol (5 – 8). All these lipid compounds involve key enzymes that has been localized in peroxisomes (9–12).