Chlorophyll Degrading Enzymes in Radish (Raphanus sativus L.) Cotyledon Chloroplasts and Their Changes in Activities with Senescence

Abstract

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 Chl degrading peroxidase activity occurred. Chl 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 Chl degrading peroxidase decreased. These findings indicate that chlorophyllase catabolizes Chl a in the chloroplasts ; Chl degrading peroxidase and Chl oxidase, especially the former, are involved in the degradation of Chl a catabolites outside the chloroplasts.