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Hexadecanoid Pathway in Plants: Lipoxygenase Dioxygenation of (7Z,10Z,13Z)-Hexadecatrienoic Acid

E. V. Osipova1, N. V. Lantsova1, I. R. Chechetkin1, F. K. Mukhitova1, M. Hamberg2, and A. N. Grechkin1*

1Kazan Institute of Biochemistry and Biophysics, Kazan Research Center, Russian Academy of Sciences, ul. Lobachevskogo 2/31, 420111 Kazan, Russia; fax: (843) 238-7577; E-mail: grechkin@mail.knc.ru

2Department of Medical Biochemistry and Biophysics, Division of Physiological Chemistry II, Karolinska Institutet, SE 171 77 Stockholm, Sweden; fax: 46-873-60439; E-mail: mats.hamberg@mbb.ki.se

* To whom correspondence should be addressed.

Received December 22, 2009; Revision received January 29, 2010
7,10,13-Hexadecatrienoic acid (16:3) is abundant in many plant species. However, its metabolism through the lipoxygenase pathway is not sufficiently understood. The goal of present work was to investigate the oxygenation of 16:3 by different plant lipoxygenases and to study the occurrence of oxygenated derivatives of 16:3 in plant seedlings. The recombinant maize 9-lipoxygenase specifically converted 16:3 into (7S)-hydroperoxide. Identification of this novel oxylipin was substantiated by data of GC-MS, LC-MS/MS, 1H-NMR, and 2D-COSY as well as by deuterium labeling from [2H6]16:3. Soybean lipoxygenase 1 produced 91% (11S)-hydroperoxide and 6% racemic 14-hydroperoxide. Recombinant soybean lipoxygenase 2 (specifically oxidizing linoleate into 13-hydroperoxide) lacked any specificity towards 16:3. Lipoxygenase 2 produced 7-, 8-, 10-, 11-, 13-, and 14-hydroperoxides of 16:3, as well as a significant amount of bis-allylic 9-hydroperoxide. Seedlings of several examined plant species possessed free hydroxy derivatives of 16:3 (HHTs), as well as their ethyl esters. Interestingly, HHTs occur not only in “16:3 plants”, but also in typical “18:3 plants” like pea and soybean seedlings.
KEY WORDS: (7Z,10Z,13Z)-hexadecatrienoic acid, lipoxygenases, oxygenation, fatty acid hydroperoxides, hexadecanoids, higher plants

DOI: 10.1134/S0006297910060052