Abstract
In early step of chlorophyll degradation, a conversion of chlorophyllide to pheophorbide occurs. Mg-dechelatase is known to involve in this step. We previously reported that low molecular substance designated as MCS (metal-chelating substance) had only activity of this reaction. In this study, to demonstrate the presence of any other substances than MCS that catalyzed Mg-dechelating reaction, Mg-dechelating activity extracted from mature leaves of Chenopodium album was examined in complete fractions after gel-filtration chromatography. The Mg-dechelating activity for chlorophyllide was detected only at MCS fractions, but the activity for Mg-chlorophyllin was found in protein and MCS fraction. We also examined peroxidase and glutathione S-transferase activity, because those enzymes were considered to be Mg-dechelatase. However, these enzymes had no activity for native substrate, chlorophyllide. This strongly suggests that MCS plays as Mg-dechelatase in the breakdown pathway of chlorophyll.
