Evolution of Chlorophyll Degradation: The Significance of RCC Reductase

Abstract

In angiosperms the key process of chlorophyll breakdown in senescing leaves is catalyzed by pheophorbide a oxygenase and RCC reductase which, in a metabolically channeled reaction, cleave the porphyrin macrocycle and produce a colourless primary catabolite, pFCC. RCC reductase is responsible for the reduction of the C20/C1 double bond of the intermediary catabolite, RCC. Depending on plant species, RCC reductase produces one of the two C1 stereoisomers, pFCC‐1 or pFCC‐2. Screening of a large number of taxa for the type of RCCR revealed that the isomer produced is uniform within families. It also revealed that type RCCR‐2 is predominant; RCCR‐1 seems to represent a recent derivation which in unrelated lineages has evolved independently from RCCR‐2. A third type of pFCC was produced by RCCR from basal pteridophytes and some gymnosperms; its structure is unknown. Collectively, the data suggest that the pathway of chlorophyll breakdown is very conserved in vascular plants. RCCR appears to represent a decisive addition to the catabolic pathway: it allows terrestrial plants to metabolize the porphyrin part of the chlorophyll molecule to photodynamically inactive final products that are stored in the vacuoles of senescing mesophyll cells.

Breakdown of chlorophyll: A nonenzymatic reaction accounts for the formation of the colorless “nonfluorescent” chlorophyll catabolites

“…The two epimeric primary FCCs set the stage for one of the two possible stereochemical lineages in Chl breakdown, which are both observed to a similar extent in higher plants (32). The absolute configuration at C-1 appears not to be altered during the subsequent catabolic transformations and the NCCs are also indicated to fall into the two groups, depending on the stereochemistry of their precursor FCC (22,32): e.g., the NCCs 1 and 3 from leaves of C. japonicum fall into the same stereochemical group as the NCCs from C. annuum and are therefore derived from a primary FCC identical to Ca-FCC-2 (2) (16,22).…”

“…The absolute configuration at C-1 appears not to be altered during the subsequent catabolic transformations and the NCCs are also indicated to fall into the two groups, depending on the stereochemistry of their precursor FCC (22,32): e.g., the NCCs 1 and 3 from leaves of C. japonicum fall into the same stereochemical group as the NCCs from C. annuum and are therefore derived from a primary FCC identical to Ca-FCC-2 (2) (16,22). Despite the indicated stereochemical divergence of the NCCs at C-1, the long wavelength parts of the CD spectra of the known natural NCCs are all similar (see, e.g., Fig.…”

Update on the biochemistry of chlorophyll breakdown

“…1). This depends on the plant species and is the result of the speciesspecific stereospecificity of red Chl catabolite reductase (RCCR) (Pružinská et al 2007;Hörtensteiner et al 2000), which introduced the C1-stereocenter during reduction of red Chl catabolite (RCC) to pFCC (see below). Thus, the occurrence of two possible stereoisomers, pFCC and epipFCC, ultimately results in C1-isomeric NCCs.…”

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.…”