Enzymes of octadecanoid biosynthesis in plants--12-oxo-phytodienoate 10,11-reductase.
Octadecanoids, potent cyclic plant signaling molecules derived from alpha-linolenic acid, are involved in the regulation of a multitude of physiological processes such as senescence, herbivore and pathogen defense, mechanoperception and morphogenesis. The first cyclic intermediate in the Vick-Zimmerman pathway of octadecanoid biosynthesis is 12-oxo-phytodienoic acid. Its conversion to the end product of the pathway, jasmonic acid, a C12 compound, first proceeds through reduction to 3-oxo-2-(pent-2'-enyl)-cyclopentane-1-octanoic acid, which is then converted to jasmonic acid by three cycles of beta-oxidation. The first of these conversions is a decisive point in the biosynthetic sequence, in that it channels the octadecanoid into the pathway of beta-oxidation. 12-Oxo-phytodienoate reductase was purified to apparent homogeneity from a cell suspension culture of Corydalis sempervirens. The enzyme is soluble and a monomer of apparent molecular mass 41 kDa which prefers NADPH over NADH to reduce the 10,11-double bond of 12-oxo-phytodienoic acid. The structure of the reaction product was proved by derivatization, GC/MS and NMR analysis. The enzyme accepts both the cis and the trans isomer of 12-oxo-phydodienoic acid, with a preference for the cis-isomer (6:1). 12-Oxo-phytodienoate reductase will also convert the synthetic substrate 2-cyclohexenone to cyclohexanone, but the enzyme did not reduce some other cyclic alpha,beta-unsaturated ketones tested (the plant hormone abscisic acid or the steroids testosterone and progesterone). Characteristic parameters of 12-oxo-phytodienoate reductase were determined.
Schaller
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Lehrstuhl für Pflanzenphysiologie, Ruhr-Universitat Bochum, Germany.
Weiler
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EW
D002478:Cells, Cultured; D002850:Chromatography, Gel; D003512:Cyclohexanones / Q000378:metabolism; D003517:Cyclopentanes / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D008401:Gas Chromatography-Mass Spectrometry; D007536:Isomerism; D010088:Oxidoreductases / Q000302:isolation & purification* / Q000378:metabolism; D044925:Oxidoreductases Acting on CH-CH Group Donors; D054883:Oxylipins; D010944:Plants / Q000201:enzymology*; D013229:Stearic Acids / Q000378:metabolism*
D003512:Cyclohexanones; D003517:Cyclopentanes; D005231:Fatty Acids, Unsaturated; D054883:Oxylipins; D013229:Stearic Acids; C028215:2-cyclohexen-1-one; C036468:cyclohexanone; C025999:12-oxophytodienoic acid; C011006:jasmonic acid; D010088:Oxidoreductases; D044925:Oxidoreductases Acting on CH-CH Group Donors; C106360:12-oxophytodienoate reductase