Peroxisomes

Abstract

Peroxisomes are single membrane bound organelles that contain catalase and at least one peroxide-generating enzyme (Huang et al. 1983). In plant cells, four different kinds of functions are described for peroxisomes and each with its own unique set of enzymes. In green tissues, the primary function of the peroxisomes is in photorespiration, where the characteristic enzyme glycolate oxidase is found. These peroxisomes occur in close association with the chloroplasts. In oil seed cotyledons, malate synthase and isocitrate lyase are predominant enzyme of glyoxylate metabolism; these peroxisiomes are sometimes called glyoxysomes to indicate their unique metabolism. Glyoxysomes are often found tightly appressed to oil bodies. In nodules of ureide-exporting species, peroxisomes are a prominent component of uninfected cells in the nodule and contain urate oxidase. Peroxisomes are also present in an unspecialized form and are often associated with the division plate Collings et al. 2003. Generally these unspecialized peroxisomes are smaller than those with specialized functions. Although peroxisomes can have no other internal structure, frequently amorphous or crystalline aggregates are noted in the peroxisomal matrix.