†Present address: Department of Botany, Stockholm University, S-10691 Stockholm, Sweden.
Identification of an allene oxide synthase (CYP74C) that leads to formation of α-ketols from 9-hydroperoxides of linoleic and linolenic acid in below-ground organs of potato
Article first published online: 8 AUG 2006
The Plant Journal
Volume 47, Issue 6, pages 883–896, September 2006
How to Cite
Stumpe, M., Göbel, C., Demchenko, K., Hoffmann, M., Klösgen, R. B., Pawlowski, K. and Feussner, I. (2006), Identification of an allene oxide synthase (CYP74C) that leads to formation of α-ketols from 9-hydroperoxides of linoleic and linolenic acid in below-ground organs of potato. The Plant Journal, 47: 883–896. doi: 10.1111/j.1365-313X.2006.02843.x
- Issue published online: 8 AUG 2006
- Article first published online: 8 AUG 2006
- Received 24 March 2006; revised 21 May 2006; accepted 26 May 2006.
- Solanum tuberosum;
- cytochrome P450;
- lipid peroxidation;
- oxylipin metabolism;
- sprouting eyes;
- substrate specificity
Allene oxide synthase (AOS) enzymes are members of the cytochrome P450 enzyme family, sub-family CYP74. Here we describe the isolation of three cDNAs encoding AOS from potato (StAOS1–3). Based on sequence comparisons, they represent members of either the CYP74A (StAOS1 and 2) or the CYP74C (StAOS3) sub-families. StAOS3 is distinguished from the other two AOS isoforms in potato by its high substrate specificity for 9-hydroperoxides of linoleic and linolenic acid, compared with 13-hydroperoxides, which are only poor substrates. The highest activity was shown with (9S,10E,12Z)-9-hydroperoxy-10,12-octadecadienoic acid (9-HPODE) as a substrate. This hydroperoxide was metabolized in vitro to α- and γ-ketols as well as to the cyclopentenone compound 10-oxo-11-phytoenoic acid. They represent hydrolysis products of the initial StAOS3 product 9,10-epoxyoctadecadienoic acid, an unstable allene oxide. By RNA gel hybridization blot analysis, StAOS3 was shown to be expressed in sprouting eyes, stolons, tubers and roots, but not in leaves. StAOS3 protein was found in all organs tested, but mainly in stems, stolons, sprouting eyes and tubers. As in vivo reaction products, the α-ketols derived from 9-hydroperoxides of linoleic and linolenic acid were only found in roots, tubers and sprouting eyes. Immunolocalization showed that StAOS3 was associated with amyloplasts and leucoplasts.