Detection of a pathway from linoleate to a novel cyclopentenone: cis-12-oxo-10-phytoenoic acid in sunflower roots.
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 (9Z,11E)-13-oxooctadeca-9,11-dienoic acid. The second pathway, which is controlled by allene oxide synthase, leads to the formation of an alpha-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 alpha-ketol are formed through the unstable allene oxide intermediate, (9Z)-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.
Grechkin
Alexander N
AN
Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences, P.O. Box 30, Kazan 420111, Russia. grechkin@mail.knc.ru
Ogorodnikova
Anna V
AV
Gnezdilov
Oleg I
OI
Mukhtarova
Lucia S
LS
D003517:Cyclopentanes / Q000737:chemistry*; D005231:Fatty Acids, Unsaturated / Q000096:biosynthesis / Q000737:chemistry*; D006368:Helianthus / Q000737:chemistry / Q000378:metabolism*; D019787:Linoleic Acid / Q000737:chemistry / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D015394:Molecular Structure; D018517:Plant Roots / Q000737:chemistry / Q000378:metabolism*; D015398:Signal Transduction; D013997:Time Factors
C526312:12-oxo-phytoenoic acid; D003517:Cyclopentanes; D005231:Fatty Acids, Unsaturated; D019787:Linoleic Acid; C013905:cyclopentenone