Crystal Structures of the Substrate-Bound Forms of Red Chlorophyll Catabolite Reductase: Implications for Site-Specific and Stereospecific Reaction

The disappearance of chlorophyll is a visual sign of fruit ripening. Yet, chlorophyll breakdown in fruit has hardly been explored; its non-green degradation products are largely unknown. Here we report the analysis and structure elucidation of colorless tetrapyrrolic chlorophyll breakdown products in commercially available, ripening bananas (Musa acuminata, Cavendish cultivar). In banana peels, chlorophyll catabolites were found in an unprecedented structural richness: a variety of new fluorescent chlorophyll catabolites (FCCs) and nonfluorescent chlorophyll catabolites (NCCs) were detected. As a rule, FCCs exist only "fleetingly" and are hard to observe. However, in bananas several of the FCCs (named Mc-FCCs) were persistent and carried an ester function at the propionate side-chain. NCCs were less abundant, and exhibited a free propionic acid group, but functional modifications elsewhere. The modifications of NCCs in banana peels were similar to those found in NCCs from senescent leaves. They are presumed to be introduced by enzymatic transformations at the stage of the mostly unobserved, direct FCC-precursors. The observed divergent functional group characteristics of the Mc-FCCs versus those of the Mc-NCCs indicated two major "late" processing lines of chlorophyll breakdown in ripening bananas. The "last common precursor" at the branching point to either the persistent FCCs, or towards the NCCs, was identified as a temporarily abundant "secondary" FCC. The existence of two "downstream" branches of chlorophyll breakdown in banana peels, and the striking accumulation of persistent Mc-FCCs call for attention as to the still-elusive biological roles of the resulting colorless linear tetrapyrroles.

show abstract

“…[30] A representative of the class-1 RCCRs was expressed from Arabidopsis, [54] and its crystal structure was deduced recently. [55,56]…”

Section: Discussionmentioning

confidence: 99%

Structures of Chlorophyll Catabolites in Bananas (Musa acuminata) Reveal a Split Path of Chlorophyll Breakdown in a Ripening Fruit

Moser

Müller

Holzinger

et al. 2012

Chemistry A European J

View full text Add to dashboard Cite

show abstract

“…This analysis identified phenylalanine 218 of AtRCCR as crucial for stereospecificity; when changed to valine (as present in tomato RCCR), AtRCCR was switched from pFCC to epipFCC production (Pružinská et al 2007). Interestingly, phenylalanine 218 is located within the RCC binding pocket in the crystal structure of AtRCCR (Sugishima et al 2009), but structure analysis of the variant with valine at position 218 did not convincingly explain the altered stereospecificity (Sugishima et al 2010).…”

Section: Red Chlorophyll Catabolite Reductasementioning

confidence: 96%

“…RCCR is a soluble protein of about 30 kDa and, like for PAO, electrons are supplied from reduced ferredoxin. RCCR is distantly related to a family of ferredoxin-dependent bilin reductases (FDBR) (Frankenberg et al 2001) and the recent elucidation of the crystal structures of Arabidopsis RCCR (AtRCCR) in the absence and presence of RCC confirmed a high degree of structural similarity to these FDBRs (Sugishima et al 2009(Sugishima et al , 2010. For the FDBRs, a reaction mechanism has been proposed that involves direct transfer of an electron from ferredoxin to the substrate giving rise to a tetrapyrrole radical intermediate, followed by substrate protonation through a highly conserved glutamate residue present in the FDBRs (Tu et al 2004(Tu et al , 2008.…”

Section: Red Chlorophyll Catabolite Reductasementioning

confidence: 98%

Update on the biochemistry of chlorophyll breakdown

2012

View full text Add to dashboard Cite

In land plants, chlorophyll is broken down to colorless linear tetrapyrroles in a highly conserved multi-step pathway. The pathway is termed the 'PAO pathway', because the opening of the chlorine macrocycle present in chlorophyll catalyzed by pheophorbide a oxygenase (PAO), the key enzyme of the pathway, provides the characteristic structural basis found in all further downstream chlorophyll breakdown products. To date, most of the biochemical steps of the PAO pathway have been elucidated and genes encoding many of the chlorophyll catabolic enzymes been identified. This review summarizes the current knowledge on the biochemistry of the PAO pathway and provides insight into recent progress made in the field that indicates that the pathway is more complex than thought in the past. Abstract In land plants, chlorophyll is broken down to colorless linear tetrapyrroles in a highly conserved multistep pathway. The pathway is termed the 'PAO pathway', because the opening of the chlorine macrocycle present in chlorophyll catalyzed by pheophorbide a oxygenase (PAO), the key enzyme of the pathway, provides the characteristic structural basis found in all further downstream chlorophyll breakdown products. To date, most of the biochemical steps of the PAO pathway have been elucidated and genes encoding many of the chlorophyll catabolic enzymes been identified. This review summarizes the current knowledge on the biochemistry of the PAO pathway and provides insight into recent progress made in the field that indicates that the pathway is more complex than thought in the past.

show abstract

“…For PcyA and HY2, a reaction mechanism has been proposed that involves a radical intermediate resulting from direct transfer of an electron from Fd to a critical (conserved) glutamate residue in the enzymes (Tu et al 2004(Tu et al , 2008 . The recent elucidation of the crystal structures of Arabidopsis RCCR in the absence or presence of RCC (Sugishima et al 2009(Sugishima et al , 2010 ) demonstrated a high degree of structural similarity to the 3D structures of PebS and PcyA (Hagiwara et al 2006 ;Dammeyer et al 2008 ) , supporting the idea that in RCCR, a radical mechanism involving a glutamate residue (glutamate 154 of Arabidopsis RCCR) is also active.…”

Section: Macrocycle Ring Openingmentioning

confidence: 85%

“…This attempt identi fi ed phenylalanine 218 , which when replaced by valine (present in tomato RCCR) switched Arabidopsis RCCR from p FCC to epi -p FCC production (Pružinská et al 2007 ) . Interestingly, this residue is located within the RCC binding pocket in the crystal structure (Sugishima et al 2009 ) , but 3D structure analysis of the phenylalanine 218 -to-valine variant did not convincingly explain the altered stereospeci fi city (Sugishima et al 2010 ) .…”

Section: Macrocycle Ring Openingmentioning

confidence: 91%

The Pathway of Chlorophyll Degradation: Catabolites, Enzymes and Pathway Regulation

Hörtensteiner

2013

Plastid Development in Leaves During Growth and Senescence

View full text Add to dashboard Cite

Crystal Structures of the Substrate-Bound Forms of Red Chlorophyll Catabolite Reductase: Implications for Site-Specific and Stereospecific Reaction

Cited by 25 publications

References 47 publications

Structures of Chlorophyll Catabolites in Bananas (Musa acuminata) Reveal a Split Path of Chlorophyll Breakdown in a Ripening Fruit

Structures of Chlorophyll Catabolites in Bananas (Musa acuminata) Reveal a Split Path of Chlorophyll Breakdown in a Ripening Fruit

Update on the biochemistry of chlorophyll breakdown

The Pathway of Chlorophyll Degradation: Catabolites, Enzymes and Pathway Regulation

Contact Info

Product

Resources

About