THE SYNTHESIS AND TURNOVER OF RAT LIVER PEROXISOMES : II. Turnover of Peroxisome Proteins

After preliminary experiments had established that the injection of Triton WR-1339 necessary for the separation of lysosomes and peroxisomes did not affect the turnover rate of catalase, the decay of (3)H-leucine incorporated into peroxisomes was studied in whole particles and in protein subfractions. It was shown that peroxisomes are destroyed in a completely random way, probably as wholes since the apparent half-life was the same for all subfractions, about 3½ days. In agreement with the results of Price et al. (11), the half-life of catalase derived from the rate of recovery from aminotriazole inhibition was about 11½ days, as was the apparent half-life of the heme prosthetic groups measured with (14)C-α-aminolevulinic acid. Guanidino-labeled arginine gave an apparent half-life of 2½ days with large statistical uncertainty. Either the leucine label was reutilized very extensively in our animals and the true half-life of peroxisomes is 1½ days, or the prosthetic groups of catalase turn over more rapidly than the protein part of the molecule.