linoleic-acid and 12-oxophytodienoic-acid

Jasmonates, a collective term combining both jasmonic acid (JA) and related derivatives, are ubiquitously distributed in the plant kingdom. They are characterized as lipid-derived signal molecules which mediate a plethora of physiological functions, in particular stress responses, male fertility, and a multitude of developmental processes. In the course of JA biosynthesis, the first oxylipin with signal character, cis-(+)-12-oxo-phytodienoic acid (OPDA), is produced in a cyclization reaction catalyzed by allene oxide cyclase (AOC). This enzyme-catalyzed ring closure is of particular importance, as it warrants the enantiomeric structure at the cyclopentenone ring which in the end results in the only bioactive JA enantiomer, cis-(+)-JA. In this review, we focus on the structural and molecular mechanisms underlying the above mentioned cyclization reaction. In this context, we will discuss the crystal structure of AOC2 of Arabidopsis thaliana with respect to putative binding sites of the instable substrate, 12,13-epoxy-9(Z),11,15(Z)-octadecatrienoic acid (12,13-EOT), as well as possible intermolecular rearrangements during the cyclization reaction.

Topics: Cyclization; Cyclopentanes; Fatty Acids, Unsaturated; Intramolecular Oxidoreductases; Linoleic Acid; Models, Chemical; Models, Molecular; Molecular Structure; Oxylipins; Plant Proteins; Protein Structure, Tertiary

Green tissues of spikemoss Selaginella martensii Spring possessed the complex oxylipins patterns. Major oxylipins were the products of linoleic and α-linolenic acids metabolism via the sequential action of 13-lipoxygenase and divinyl ether synthase (DES) or allene oxide synthase (AOS). AOS products were represented by 12-oxophytodienoic acid (12-oxo-PDA) isomers. Exceptionally, S. martensii possesses high level of 12-oxo-9(13),15-PDA, which is very uncommon in flowering plants. Separate divinyl ethers were purified after micro-preparative incubations of linoleic or α-linolenic acids with homogenate of S. martensii aerial parts. The NMR data allowed us to identify all geometric isomers of divinyl ethers. Linoleic acid was converted to divinyl ethers etheroleic acid, (11Z)-etheroleic acid and a minority of (ω5Z)-etheroleic acid. With α-linolenate precursor, the specificity of divinyl ether biosynthesis was distinct. Etherolenic and (ω5Z)-etherolenic acids were the prevailing products while (11Z)-etherolenic acid was a minor one. Divinyl ethers are detected first time in non-flowering land plant. These are the first observations of fatty acid metabolism through the lipoxygenase pathway in spikemosses (Lycopodiophyta).

Topics: alpha-Linolenic Acid; Cyclopentanes; Cytochrome P-450 Enzyme System; Fatty Acids, Unsaturated; Intramolecular Oxidoreductases; Linoleic Acid; Lipoxygenase; Nuclear Magnetic Resonance, Biomolecular; Oxylipins; Plant Proteins; Selaginellaceae; Vinyl Compounds