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12-Oxophytodienoate reductase 3 (OPR3) is the isoenzyme involved in jasmonate biosynthesis
Florian Schaller, Christian Biesgen, Carsten Müssig, Thomas Altmann and Elmar W. Weiler
Vol. 210, No. 6 (May 2000), pp. 979-984
Published by: Springer
Stable URL: http://www.jstor.org/stable/23385936
Page Count: 6
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In addition to OPR1 and OPR2, two isoenzymes of 12-oxophytodienoate reductase, a third isoform (OPR3) has recently been identified in Arabidopsis thaliana (L.) Heynh. The expression of the OPR3 gene is induced not only by a variety of stimuli, such as touch, wind, wounding, UV-light and application of detergent, but also by brassinosteroids. The three enzymes were expressed in a functional form in Escherichia coli, and OPR2 was additionally expressed in insect cell cultures and overexpressed in A. thaliana. Substrate conversion was analyzed using a stereospecific assay. The results show that OPR3 effectively converts the natural (9S,13S)-12-oxophytodienoic acid [Km = 35 μM, Vmax 53.7 nkat (mg protein)-1] to the corresponding 3-2(2′(Z)-pentenyl) cyclopentane-1-octanoic acid (OPC-8:0) stereoisomer while OPR1 and OPR2 convert (9S,13S)-12-oxophytodienoic acid with greatly reduced efficiency compared to OPR3. Thus, OPR3 is the isoenzyme relevant for jasmonate biosynthesis.
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