Peroxisomes in pigment epithelium and Müller cells of amphibian retina possess D-amino acid oxidase as well as catalase.

In this paper we identify peroxisomes in Müller cells and retinal pigment epithelial cells of Rana pipiens and Xenopus laevis by virtue of their content of cytochemically stainable catalase. These organelles have the form of an extensive, branched system of tubules in the retinal pigment epithelium and appear as discrete ovoid structures in the Müller cells. In both the pigment epithelium and the Müller cells a second peroxisomal enzyme, D-amino acid oxidase, can be detected in the same structures as catalase by means of a cerium-based cytochemical staining procedure. This oxidase is active only against nonpolar and polar, uncharged D-amino acids.