title: Hydroxymethylated Dioxobilins in Senescent Arabidopsis thaliana Leaves: Sign of a Puzzling Biosynthetic Intermezzo of Chlorophyll Breakdown.
abstract: 1-Formyl-19-oxobilin-type tetrapyrroles are characteristic, abundant products of chlorophyll breakdown in senescent leaves. However, in some leaves, 1,19-dioxobilin-type chlorophyll catabolites (DCCs) lacking the formyl group accumulate instead. A P450 enzyme was identified in in vitro studies that removed the formyl group of a primary fluorescent chlorophyll catabolite (pFCC) and generated fluorescent DCCs. These DCCs are precursors of isomeric nonfluorescent DCCs (NDCCs). Here, we report a structural investigation of the NDCCs in senescent leaves of wild-type Arabidopsis thaliana. Four new NDCCs were characterized, two of which carried a stereoselectively added hydroxymethyl group. Such formal DCC hydroxymethylations were previously found in DCCs in leaves of a mutant of A. thaliana. They are now indicated to be a feature of chlorophyll breakdown in A. thaliana, associated with the specific in vivo deformylation of pFCC en route to NDCCs.
authors.affiliation: Institute of Organic Chemistry and Center for Molecular Biosciences, University of Innsbruck, Innrain 80/82, 6020 Innsbruck (Austria).
authors.forename: Iris
authors.initials: I
authors.lastname: Süssenbacher
authors.affiliation: Institute of Organic Chemistry and Center for Molecular Biosciences, University of Innsbruck, Innrain 80/82, 6020 Innsbruck (Austria).
authors.forename: Christoph R
authors.initials: CR
authors.lastname: Kreutz
authors.affiliation: Institute of Plant Biology, University of Zürich, Zollikerstrasse 107, 8008 Zürich (Switzerland).
authors.forename: Bastien
authors.initials: B
authors.lastname: Christ
authors.affiliation: Institute of Plant Biology, University of Zürich, Zollikerstrasse 107, 8008 Zürich (Switzerland).
authors.forename: Stefan
authors.initials: S
authors.lastname: Hörtensteiner
authors.affiliation: Institute of Organic Chemistry and Center for Molecular Biosciences, University of Innsbruck, Innrain 80/82, 6020 Innsbruck (Austria). bernhard.kraeutler@uibk.ac.at.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Kräutler
mesh_terms: D017360:Arabidopsis / Q000201:enzymology*; D001669:Biochemical Phenomena; D002734:Chlorophyll / Q000737:chemistry* / Q000378:metabolism; D015394:Molecular Structure; D018515:Plant Leaves / Q000737:chemistry*; D011758:Pyrroles / Q000737:chemistry*; D045725:Tetrapyrroles / Q000737:chemistry* / Q000378:metabolism
chemical_list: D011758:Pyrroles; D045725:Tetrapyrroles; C000590876:dioxobilin; D002734:Chlorophyll
keywords: biosynthesis; chlorophyll; phyllobilin; structure elucidation; tetrapyrrole