Figure 7.
Topographical model of Chl-breakdown in senescent leaves of broccoli, according to the “PAO/phyllobilin-pathway”.7,8 The early steps of this pathway take place in the chloroplast/gerontoplast.7 The model is based on the current tentative view of the subcellular localization of Chl-catabolites,41 and Chl-catabolic enzymes of the further pathway are specified, based on presumed modifications of breakdown intermediates, as deduced from the structures of colorless Chl-catabolites identified in the present work. Putative catabolites are labeled with asterisk (*), putative enzyme catalyzed steps are specified by a general label for the enzyme class of a methylesterase (a), for a deformylating cytochrome (b) and of a glycosidase (c) (see Figure 6 for chemical formulas of the suggested intermediate FCCs and of the nonfluorescent catabolites Bo-NCC-1 (1), Bo-NCC-2 (2), and Bo-DNCC (3)).