Chlorophyll degrading enzymes in radish (Raphanus sativus L.) cotyledon chloroplasts and their changes in activities with senescence

Chlorophyll (Chl) degrading enzymes in radish (Raphanus sativus L.) cotyledon chloroplasts and their changes in activities with senescence were studied. Most chlorophyllase activity was localized in the chloroplast where little Chi degrading peroxidase activity occurred. Chi oxidase activity was localized both inside and outside the chloroplast. Chlorophyllase activity in chloroplasts increased while the cotyledons senesced; whereas oxidative enzyme activities, especially those of Chi degrading peroxidase decreased. These findings indicate that chlorophyllase catabolizes Chi a in the chloroplasts; Chi degrading peroxidase and Chi oxidase, especially the former, are involved in the degradation of Chi a catabolites outside the chloroplasts.