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SUMMARY:A cytochrome P450 monooxygenase is involved in chlorophyll breakdo
 wn in Arabidopsis thaliana - Stefan Hörtensteiner\, University of Zürich
DTSTART:20120522T120000Z
DTEND:20120522T130000Z
UID:TALK38238@talks.cam.ac.uk
CONTACT:28552
DESCRIPTION:\nNonfluorescent chlorophyll catabolites (NCCs) have been desc
 ribed as end products of chlorophyll breakdown in Arabidopsis [1]. NCCs ar
 e open tetrapyrroles formed from respective fluorescent precursors\, terme
 d FCCs\, through acid-catalyzed isomerization after import of FCCs into th
 e vacuoles of senescing cells.\n\nI present an overview on the current kno
 wledge of the pathway of chlorophyll degradation. In addition\, I provide 
 evidence for physical interaction at the thylakoid membrane between the en
 zymes required for conversion of chlorophyll to a primary FCC. This intera
 ction infers that metabolic channeling of breakdown intermediates occurs\,
  most likely to minimize the risk of toxicity of these potentially photody
 namic intermediates.\n\nIn Arabidopsis\, quantification of NCCs in senesce
 nt leaves had implied that their amount might correspond to the pool of ch
 lorophyll present in green leaves. I present genetic and biochemical evide
 nce for a cytochrome P450 monooxygenase to be involved in the formation of
  a new type of chlorophyll catabolites in Arabidopsis. Mutants of this P45
 0 (cyp-1) accumulate much more NCCs than wild-type plants. Analysis of chl
 orophyll catabolite profiles of wild-type and cyp-1 mutants identified nov
 el catabolites in wild-type that are absent in the mutants\; these new cat
 abolites\, tentatively named urobilinogenoidic nonfluorescent chlorophyll 
 catabolites (uNCCs)\, account for more than 90% of broken-down chlorophyll
 \, while NCCs only represent a minor fraction. In summary\, I propose that
  a cytochrom P450 monoxygenase is involved in chlorophyll breakdown in Ara
 bidopsis. Moreover\, due to the 10-fold increase of NCCs in cyp-1 mutants\
 , I propose\, in contrast to earlier finding\, that uNCCs not NCCs represe
 nt the majority of the chlorophyll catabolites that accumulate in Arabidop
 sis.\n\n[1] Hörtensteiner\, S.\; Kräutler\, B. (2011) Chlorophyll breakd
 own in higher plants. Biochim. Biophys. Acta 1807: 977-988
LOCATION:Large Lecture Theatre\, Department of Plant Sciences
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