Tracking Down Chlorophyll Breakdown in Plants: Elucidation of the Constitution of a “Fluorescent” Chlorophyll Catabolite

Abstract

The biological enigma of the breakdown of chlorophyll in plants only recently began to be understood. The structure elucidation of a “fluorescent” catabolite (depicted on the right) from senescent rape cotyledons provides further insight into this process. For this purpose, the catabolite was prepared from pheophorbide a with an enzyme extract from senescent choloroplasts.

Chlorophyll Breakdown in Senescent Chloroplasts (Cleavage of Pheophorbide a in Two Enzymic Steps)

“…Recently, the structure of this apparently primary catabolite of Pheide a has been determined ( Fig. 1; Miihlecker et al, 1997). The conversion of Pheide a into Bn-FCC-2 formally involves the introduction of two atoms of oxygen (opening of the macrocycle in the C4/ C5 mesoposition) as well as of four atoms of hydrogen (reduction of double bonds of the p-and 6-methine bridges).…”

A novel blue fluorescent chlorophyll catabolite accumulates in senescent leaves of the peace lily and indicates a split path of chlorophyll breakdown

“…Chlbreakdown in Sp. wallisii was thus indicated to (involve red Chlcatabolite reductase RCCR-1 [27] and to) pass through the stage of pFCC [10]. In contrast, in peels of ripening bananas, the complementary stereo-chemical lineage was revealed [28], which passes the stage of epi-pFCC [11], the C(1)-epimer of pFCC.…”

“…However, HPLC-analysis indicated Sw-NCC-58 and Cj-NCC-1 to be different. The structural mismatch between Sw-NCC-58 and Cj-NCC-1 was thus assigned to the stereochemistry at C(1) [10,11], classifying these two NCCs as C(1)-epimers.…”

“…Minute amounts of fluorescent compounds were observed earlier during active stages of leaf de-greening as presumed Chl-breakdown products [9]. Two of these were identified as FCCs, unstable precursors of NCCs [10,11]. In banana peels (Musa acuminata) and in senescent banana leaves, accumulation of 'persistent' FCCs was discovered recently [12][13][14].…”

The Mechanism of Chlorophyll Degradation in Plants

“…[1] Nowadays the path of Chl breakdown is largely resolved, including the structure elucidation of catabolites and the cloning of genes from catabolic enzymes. [2,3] The structures of colorless Chl catabolites (NCCs) from leaves and fruits of various plant species exhibit a common backbone with an oxygenolytically opened chlorin ring. All remaining mesocarbons are saturated and as a consequence NCCs do not absorb visible light.…”