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Jasmonates are derived from oxygenated fatty acids (oxylipins) via the octadecanoid pathway and are characterized by a pentacyclic ring struc-ture. They have regulatory functions as signaling molecules in plant devel-opment and adaptation to environmental stress. | ễFEBS Journal The allene oxide cyclase family of Arabidopsis thaliana - localization and cyclization Florian Schaller1 Philipp Zerbe1 Steffen Reinbothe1 Christiane Reinbothe2 Eckhard Hofmann3 and Stephan Pollmann1 1 Lehrstuhl fur Pflanzenphysiologie Ruhr-Universitat Bochum Germany 2 Lehrstuhl fur Pflanzenphysiologie Universitat Bayreuth Germany 3 Lehrstuhl fur Biophysik AG Rontgenstrukturanalyse an Proteinen Ruhr-Universitat Bochum Germany Keywords 12-oxo-phytodienoic acid allene oxide cyclase allene oxide synthase oxylipins signaling Correspondence S. Pollmann Lehrstuhlfur Pflanzenphysiologie Ruhr-Universitat Bochum Germany Fax 49 234 32 14187 Tel 49 234 32 24294 E-mail stephan.pollmann@rub.de These authors contributed equally to this work Received 12 December 2007 revised 24 January 2008 accepted 10 March 2008 doi 10.1111 j.1742-4658.2008.06388.x Jasmonates are derived from oxygenated fatty acids oxylipins via the octadecanoid pathway and are characterized by a pentacyclic ring structure. They have regulatory functions as signaling molecules in plant development and adaptation to environmental stress. Recently we solved the structure of allene oxide cyclase 2 AOC2 of Arabidopsis thaliana which is together with the other three AOCs a key enzyme in the biosynthesis of jasmonates in that it releases the first cyclic and biologically active metabolite - 12-oxo-phytodienoic acid OPDA . On the basis of models for the bound substrate 12 13 S -epoxy-9 Z 11 15 Z -octadecatrienoic acid and the product OPDA we proposed that a conserved Glu promotes the reaction by anchimeric assistance. According to this hypothesis the transition state with a pentadienyl carbocation and an oxyanion is stabilized by a strongly bound water molecule and favorable p-p interactions with aromatic residues in the cavity. Stereoselectivity results from steric restrictions to the necessary substrate isomerizations imposed by the protein environment. Here site-directed mutagenesis was used to explore
