Localization of Catalase A in Vacuoles ofSaccharomyces cerevisiae:Evidence for the Vacuolar Nature of Isolated "Yeast Peroxisomes"

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Abstract
The enzyme was bound to large particles, whereas most of the activity of catalase T was located in a 38,000 .times. g supernatant. Under various isolation conditions, catalase A always showed a distribution among subcellular fractions virtually identical to that of 2 markers for vacuoles, proteinase B and .alpha.-mannosidase. More than 80% of the catalase A activity of a crude vacuole fraction has been detected in purified vacuoles. Malate synthase, isocitrate lyase and glyoxylate reductase (NADP+), 3 peroxisomal markers, showed a subcellular distribution significantly different from that of catalase A. Catalase A may be specifically associated with the vacuoles of yeast. Like vacuoles, peroxisomal fractions isolated from yeast spheroplasts as described by Avers contain only 1 catalase protein, catalase A. Isopycnic and sedimentation velocity separations of crude mitochondrial fractions showed that catalase A in peroxisomal fractions is accompanied by considerable activities of proteinase B and .alpha.-mannosidase. It seems that the catalase-active particles isolated under such conditions are not typical peroxisomes but vesicles formed from vacuoles during the isolation procedure.

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