Absence of DNA in peroxisomes of Candida tropicalis

Yeast peroxisomes were purified to near homogeneity from cells of Candida tropicalis grown on oleic acid for the purpose of examining the possible presence of DNA in this organelle. The purification procedure includes the effective conversion of cells to spheroplasts with Zymolyase and sodium sulfite and the separation of the organelles at extremely low ionic strength. The mitochondrial contamination was less than 1%, based on several criteria, and the yield of peroxisomes was about 40%. The purified peroxisomal fraction contained a very small amount of DNA, which yielded restriction fragments indistinguishable from those of mitochondrial DNA. The absence of DNA in peroxisomes was also supported by cesium chloride density gradient centrifugation of the organelles lysed with a detergent, staining of the organelles with a fluorescent dye specific to DNA, and labeling of the DNA with [3H]adenine.