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Detection of a Pathway From Linoleate to a Novel Cyclopentenone: cis ‐12‐Oxo‐10‐Phytoenoic Acid in Sunflower Roots
Author(s) -
Grechkin Alexander N.,
Ogorodnikova Anna V.,
Gnezdilov Oleg I.,
Mukhtarova Lucia S.
Publication year - 2007
Publication title -
chembiochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.05
H-Index - 126
eISSN - 1439-7633
pISSN - 1439-4227
DOI - 10.1002/cbic.200700393
Subject(s) - allene , cyclopentenone , linoleic acid , chemistry , biosynthesis , sunflower , lipoxygenase , methyl jasmonate , atp synthase , stereochemistry , germination , enzyme , biochemistry , biology , botany , fatty acid , gene , catalysis , agronomy
The lipoxygenase pathway in sunflower roots was studied in vitro. A preliminary incubation of linoleic acid with 15 000 g supernatant of homogenate of sunflower roots (1.5–6 days after germination) revealed the predominant activity of 13‐lipoxygenase. The exogenously added linoleic acid 13‐hydroperoxide is further utilized through two competing pathways. One of them is directed towards formation of the ketodiene (9 Z ,11 E )‐13‐oxooctadeca‐9,11‐dienoic acid. The second pathway, which is controlled by allene oxide synthase, leads to the formation of an α‐ketol and a novel cyclopentenone, rac‐cis‐ 12‐oxo‐10‐phytoenoic acid (12‐oxo‐PEA) via a short‐lived allene oxide. Unexpectedly, the cyclopentenone 12‐oxo‐PEA is the predominant allene oxide synthase product. Identification of cis ‐12‐oxo‐PEA was confirmed by its UV, mass, 1 H NMR and 2D‐COSY spectral data. The highest yield of 12‐oxo‐PEA is observed in very young roots (1.5–2 days after germination). The results of methanol‐trapping experiments demonstrate that both 12‐oxo‐PEA and α‐ketol are formed through the unstable allene oxide intermediate, (9 Z )‐12,13‐epoxyoctadeca‐9,11‐dienoic acid, which is the primary product of allene oxide synthase. Since 12‐oxo‐PEA is a jasmonate congener, its biosynthesis in plants might be of physiological importance.