TY - CHAP M1 - Book, Section TI - Peroxisome Disorders A1 - Wangler, Michael A1 - Rizzo, William B. A1 - Braverman, Nancy A2 - Kline, Mark W. Y1 - 2018 N1 - T2 - Rudolph's Pediatrics, 23e AB - Peroxisomes are single membrane-bound organelles present in virtually all eukaryotic cells that number between hundreds to a few thousand per cell. Peroxisomes appear on electron micrographs as spherical organelles (Fig. 157-1) and contain a dense proteinaceous matrix composed of over 50 enzymes. Peroxisomes are involved in a diverse list of metabolic processes, but the most well characterized are the enzymatic β-oxidation of very-long-chain fatty acids and other substrates, biosynthesis of plasmalogens and bile acids, α-oxidation of branched chain fatty acids (phytanic acid), and glyoxylate and lysine degradation. Furthermore, catalase and other antioxidant enzymes in peroxisomes play a role in regulating the cellular redox balance. Peroxisomes form through the concerted action of an evolutionarily conserved protein machinery encoded by the PEX genes (Table 157-1). The PEX gene products orchestrate a process of de novo peroxisome biogenesis that begins with designation of membrane compartment, derived from the endoplasmic reticulum. In addition to de novo peroxisome biogenesis, peroxisomes can form from existing peroxisomes through fission, and recent studies have suggested that fission may play at least as important a role in creating new peroxisomes as de novo biogenesis. SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/11/09 UR - accesspediatrics.mhmedical.com/content.aspx?aid=1182929681 ER -