ENZYMATIC DEGRADATION OF CHLOROPHYLL IN CHENOPODIUM-ALBUM

The breakdown of chlorophyll (Chl) in crude extracts of Chenopodium album (white goose foot) in the dark was examined. Derivatives of pheophorbide a were formed when Chl a or chlorophyllide a was incubated with depigmented crude extracts. The formation of pheophrobide was completely prevented by heat treatment of extracts, indicating that the reaction was enzymatic, and the presence of a Mg-releasing enzyme, the so called Mg-dechelatase, was postulated. This hypothesis was strongly supported by the observation that the formation of pheophorbide was inhibited by 51% by 10 mM MgCl2. Analysis by high-performance thin-layer chromatography (HPTLC) and liquid chromatography (HPLC) showed that the appearance of chlorophyllide a, pheophorbide a, 13(2)-hydroxychlorophyllide a and pyropheophorbide a was accompanied by a concomitant decrease in levels of Chl a. The formation of 13(2)-hydroxychlorophyllide a was not clearly an enzymatic reaction and requires further examination. It appears that Chl a is degraded in a crude extract of C. album via the following enzymatically catalyzed reactions: Chl a-->chlorophyllide a-->pheophorbide a-->pyropheophorbide a. -phytyl -Mg -COOCH3.