Which of the following statements is false regarding peroxisomes?
Peroxisomes are single-membrane organelles morphologically and functionally distinct from lysosomes despite both participating in degradative metabolism. Transmission electron microscopy shows spherical vesicles 0.1 to 1 micrometer with electron-dense crystalline cores composed of urate oxidase in rat or dense catalase aggregates in humans. Unlike double-membrane mitochondria and nucleus, peroxisomes are bounded by single phospholipid bilayer enriched in peroxisomal membrane proteins PMP70, ALDP, PEX11 isoforms and containing import translocon. Their matrix contains oxidative enzymes such as acyl-CoA oxidases, D-amino acid oxidase, L-pipecolic acid oxidase and catalase that generate and decompose hydrogen peroxide via dehydrogenation reactions, not classic acid hydrolases that cleave bonds at low pH using water. Biogenesis studies using live-cell imaging, vesicle budding assays and Sec16B colocalization demonstrate that pre-peroxisomal vesicles bud from specialized subdomains of endoplasmic reticulum carrying PEX3, PEX16 and PEX19, then fuse heterotypically and mature via growth and division mediated by PEX11 beta that elongates membrane and DRP1 and Fis1 that constrict and split. Therefore de novo formation coexists with growth and fission of pre-existing peroxisomes, firmly establishing ER contribution, while claim of exclusively containing hydrolytic enzymes reflects outdated confusion with lysosomes.
Ref: Smith & Aitchison, Cold Spring Harbor Perspect Biol 2013: Peroxisomes Originate from ER and Contain Oxidases.