Breakdown of chlorophyll:: A fluorescent chlorophyll catabolite from sweet pepper (Capsicum annuum)

The primary fluorescent chlorophyll catabolite 1(Ca-FCC-2) from sweet pepper (Capsicum annuum) has similar optical properties, but is slightly less polar than the primary FCC (pFCC; 2) from senescent cotyledons of oilseed rape (Brassica napus). Ca-FCC-2 was prepared from pheophorbide a using an enzyme extract from ripe C. annuum chromoplasts. The catabolite Ca-FCC-2 (1) could be determined from fast-atom-bombardment (FAB) mass spectra to be an isomer of pFCC (2). The constitution of Ca-FCC-2 was determined by homo- and heteronuclear magnetic-resonance experiments and was found to be identical to that of pFCC. Further 2D-homonuclear spectra of Ca-FCC-2 revealed it to differ from pFCC by the configuration at the methine atom C(lj, whose configuration results from the action of red chlorophyll catabolite reductase (RCCR). The occurrence of two primary FCCs that are epimeric at C(1) provides a structural basis for the recent observation of two types of RCCRs among higher plants.