Chlorophyll Catabolites and the Biochemistry of Chlorophyll Breakdown

Abstract

Although chlorophyll synthesis in Spring and its degradation in Autumn are undoubtedly the most colorful manifestations of life on Earth, chlorophyll catabolism remained an enigma until about fi fteen years ago. Contrary to expectation, chlorophyll breakdown in vascular plants rapidly leads to colorless degradation products and only fl eetingly involves colored intermediates, which result from enzymatic oxidative opening of the chlorophyll macrocycle. This key oxygenolytic step in higher plants is rapidly followed by an enzymatic reduction to form short-lived fl uorescent catabolites. These latter tetrapyrroles isomerize rapidly in an acid-catalyzed chemical step to colorless tetrapyrrolic catabolites. The colorless and non-fl uorescent bilanones fi nally accumulate in the vacuoles of the degreened plant tissues. This chapter outlines the structural features of chlorophyll catabolites from natural sources and the biochemistry of chlorophyll breakdown.