Peroxisomes and Peroxisomal Disorders

Abstract

Peroxisomes are organelles that are present in virtually all human cell types. The diameter varies between 0.15 and 1.5 µm. Morphologically peroxisomes are differentiated from mitochondria by their single membrane, electron-dense homogeneous matrix and the absence of cristae and from lysosomes which often contain vacuoles, lipids, myelin figures, or other inclusions and have a positive acid phosphatase reaction in histochemistry. It has been demonstrated that peroxisomes contain enzymes for a simple respiratory pathway: oxidases, and catalase. The oxidases produce hydrogen peroxide as a reaction product, which is a very toxic metabolite. It is subsequently reduced by catalase to water by either a peroxidatic or catalatic mechanism. The term peroxisome has been introduced to emphasize these properties. These properties permitted the use of 3,3’-diaminobenzidine as a hydrogen donor in the peroxidatic reaction of catalase, a technique that makes it possible to stain these organelles for light and electron microscopy.