Enzymic degradation of chlorophyll in cavendish bananas : In vitro evidence for two independent degradative pathways

摘要: The Breakdown of chlorophyll a was examined in soluble and Triton-solubilized enzyme extracts from Cavendish bananas (Musa cavendishi) ripened at ambient temperature (30-34°C). Chl efficiently degraded by both the fractions solubilization Triton, however, exhibited 2 fold higher activity over that extract. Mg-dechelatase catalyzed dechelation Mg chlorophyllin extract showed than solubilized dechelatase inhibited presence NgCl2. catabolic under anoxygenic conditions ascorbate suggesting existence oxygen-independent oxygen-dependent processes degradation. Linoleic acid stimulated degradation process indicating oxidase. Catalase also stimulation activity. Hydrogen peroxide (H O ) superoxide dismutase resulted inhibition. inhibition H restored dichlorophenulinduphenol (DCIP). These results suggest apart dephytylating chlorophyllase pathway, catalyze oxidative enzymes involving active oxygen Ten different intermediates enzymic were detected RP-HPLC. dephytylated polar intermediate, chlorophyllide a, pheophorbide pyropheophorbide probably hydroxy-pheophorbide appeared disappeared during time course reaction operation mediated Type I 13 -hydroxy-Chl as primary product first oxidase, along with hydroxy-lactone-Chl an unknown intermediate involvement other bleaching pathway. reveal crude degrade two distinct pathways - Chlorophyllase pathway