TAILIEUCHUNG - Báo cáo khoa học: The allene oxide cyclase family of Arabidopsis thaliana – localization and cyclization

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 These authors contributed equally to this work Received 12 December 2007 revised 24 January 2008 accepted 10 March 2008 doi 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

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