25. Self-Sustaining Chemical        Systems: Living Cells   Previous PageNext Page
       Lysosomes and Peroxides

In the face of general bafflement as to the purpose of peroxisomes, an ingenious theory has been proposed, according to which peroxisomes and catalase arose as an early defense mechanism of primitive anaerobic organisms against atmospheric oxygen. Many essential reactions in a cell lead to reduced flavoproteins, which then are reoxidized by anaerobic means. Traces of oxygen in the surroundings of an anaerobe could upset things by reoxidizing the flavoproteins directly, and producing hydrogen peroxide:

Peroxides of all kinds are reactive and dangerous oxidants, and must be removed for the safety of the cell. Catalase may have evolved to meet this need by using some expendable organic molecules (HR) as a reducing donor:

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