Peroxisomes are important cell organelles that occur in virtually all eukaryotic cells. The significance of these organelles is probably best illustrated by the identification of inherited human diseases that are related to microbody malfunctioning, some of which are lethal. Moreover,
since peroxisomal metabolism is oxidative in nature it contributes to oxidative stress and hence ageing processes. Peroxisomes are industrially relevant, since the production of the antibiotic penicillin by filamentous fungi like Penicillium chrysogenum requires these organelles.
The function of peroxisomes is highly variable and depends on organism, tissue and developmental stage.
Peroxisiomes generally contain hydrogen peroxide producing oxidases together with catalase, which decomposes hydrogen peroxide. Also the beta oxidation of fatty acids is a common peroxisomal pathway.
The formation of peroxisomes (biogenesis) occurs via unique molecular mechanisms. Unravelling these mechanisms greatly contributes to fundamental knowledge in the heart of molecular cell biology. Because of the strong conservation of these processes, knowledge obtained in a yeast model system can readily be translated to higher eukaryotes including man.
We use baker’s yeast (Saccharomyces cerevisiae), the methylotrophic yeasts Hansenula polymorpha and Pichia pastoris as well as the filamentous fungus Penicillium chrysogenum as model organisms to study peroxisomes at the molecular level.
Yeasts are ideal models for peroxisome research because they are easy to cultivate and readily accessible to advanced molecular, biochemical and ultrastructural methods. Furthermore, proliferation or autophagic degradation of peroxisomes in yeast can readily be prescribed by manipulation of the growth conditions. For molecular approaches, a key advantage is the viability of mutants defective in peroxisome biogenesis (Pex
-
-mutants) and degradation (Atg
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- mutants), allowing extensive mutational analysis of genes involved in peroxisome formation, degradation and function.
Relative to S. cerevisiae, the yeast H. polymorpha has the additional advantage that the morphological and biochemical events accompanying peroxisome proliferation and degradation are much more pronounced. For both model systems, all the necessary tools to perform detailed molecular studies are available (including the sequence of the genomes, allowing performing “omics” approaches).
