Lipoxygenase, Hydroperoxide Isomerase, and Hydroperoxide Cyclase in Young Cotton Seedlings

Abstract

Lipoxygenase was demonstrated in young cotton seedlings. It catalyzed the oxygenation of linoleic or linolenic acid, predominantly at carbon 13, and its molecular weight was estimated by gel filtration to be 100,000.Hydroperoxide isomerase was also present and converted hydroperoxylinoleic or hydroperoxylinolenic acid to a-or y-ketols. The enzyme utilized the 13-hydroperoxy isomer in preference to the 9 isomer and its molecular weight was estimated at 250,000 by gel filtration. In addition, hydroperoxide cyclase, which catalyzes the conversion of 13-hydroperoxylinolenic acid to 12-oxo-phytodienoic acid, was present. Hydroperoxide isomerase and hydroperoxide cyclase activities could not be separated by gel filtration and ion-exchange chromatography experiments, indicating the two enzyme activities may be associated with the same protein. The activities of all three enzymes were very low in the seed but increased immediately after germination, reached a maximum after 3 to 4 days, and then declined. The results suggest a role, as yet unknown, for these enzymes during early plant development.

Characterization of 12-Oxo-Phytodienoic Acid Reductase in Corn

“…However, our experience with corn ( Fig. 8) and other plants (13,14) indicates that the enzymes of the pathway usually have their highest activity in young, actively growing plant tissues. We believe that jasmonic acid has another, more subtle role in metabolism unrelated to senescence.…”

“…The first enzyme of the jasmonic acid pathway, lipoxygenase, has been the subject of several reviews (1, 5, 1 1). The second enzyme, hydroperoxide cyclase, is present in many plant species and its properties in cell-free extracts have also been reported (12)(13)(14)17). The third enzyme, 12-oxo-phytodienoic acid reductase, has not previously been characterized.…”

Fatty acid hydroperoxides pathways in plants. A review.

“…The molecular weight of the enzyme is 250.000 Da in cotton seedlings (Vick and Zimmerman, 1981), 220.000 in spinach leaf (Vick and Zimmerman, 1987), and 293.000 in eggplant (Grossman et al, 1983). In flaxseed, hydroperoxide lyase is described as a 55.000 Da protein (Song and Brash, 1991) suggesting that it probably exists as a tetramer.…”

“…Like hydroperoxide lyase, hydroperoxide dehydrase is a membrane bound enzyme and requires thus detergent for solubilization (Vick and Zimmerman, 1981;Vick and Zimmerman, 1987). The enzyme is routinely isolated as a microsomal pellet, but the specific identity of the membrane association has been incompletely investigated.…”

“…The optimum pH of hydroperoxide dehydrase is between 6 and 7 (Vick and Zimmerman, 1981;Grossman et al, 1983;Vick and Zimmerman, 1987;Baertshi et al, 1988). The molecular weight of the enzyme is 250.000 Da in cotton seedlings (Vick and Zimmerman, 1981), 220.000 in spinach leaf (Vick and Zimmerman, 1987), and 293.000 in eggplant (Grossman et al, 1983).…”