Oxidation of various lipid substrates with unfractionated soybean and wheat lipoxidase

Abstract

Quantitative determinations of lipoxidase in wheat were made on five milling fractions from four wheat varieties, including two hard red winter and two hard red spring wheats. Lipoxidase content decreased with increasing refinement and was lowest in the flour fraction. In general, the mill fractions from spring wheats exhibited slightly higher lipoxidase content than the corresponding mill fractions from winter wheats.Aqueous extracts from soybeans (variety Hawkeye) and wheat (variety Selkirk, break shorts fraction) were adjusted in concentration so that the lipoxidase activity with respect to linoleic acid was approximately the same. The diluted extracts were then tested for their ability to oxidize other lipid substrates with the necessary 1,4 pentadiene system. Soybean lipoxidase was far more reactive toward methyl linoleate and trilinolein than wheat lipoxidase. Mono‐ and dilinolein were relatively unreactive in both systems although dilinolein was a better substrate in the soybean system than in the wheat. Neither system oxidized highly unsaturated digalactosyl diglycerides alone. However the soybean extract oxidized this substrate to a small extent in the presence of catalytic amounts of linoleic acid while, under identical conditions, the wheat extract remained inactive.Polyacrylamide gel electrophoresis of the aqueous extracts of soybeans and wheat‐milling fractions coupled with a staining procedure specifically for lipoxidase indicated three to four isoenzyme bands in the soybeans and two to four isoenzyme bands in the wheat‐milling fractions. Isoenzymes may be responsible for differences in enzymatic activity on various substrates.

Partial Purification and Study of Some Properties of Rice Germ Lipoxygenase

“…Table II summarizes the results of a typical purification. Disc electrophoresis on 7 ~~ polyacrylamide gel 5 ) of the peak fraction obtained in the gel filtration on a Sephadex G-100 column gave one major protein band bearing Iipoxygenase activity and two trace protein bands both being negative in activity staining reaction of Guss et al 6 ) The result indicates homogeneity of the final preparation with respect to Iipoxygenase. The molecular weight of the enzyme estimated by the gel filtration method was 95,000.…”

Two soybean seed lipoxygenase nulls accumulate reduced levels of lipoxygenase transcripts

“…The LOX-1 species had been crystallized earlier by Theorell (55), while LOX-2 (11) and LOX-3 (12) were purified by Christopher et al Chromatographic refinements lead to detection of a fourth isozyme, called LOX-3b (3). These isozymes vary with respect to pH optima (3,11), heat stability (11), response to Ca 2÷ (12,62), isoelectric point (3) and substrate specificity (3,11,16,17,31). The LOX isozymes appear to contain iron as a prosthetic component (10,40,45).…”

Determination of the Activity of Lipoxygenase (Lipoxidase)

“…The distribution of isoenzymes is not limited to soybean. There are many reports in the literature describing the existence of isoenzymes in different plant sources, including peas (8&9l), fava beans (22,23), alfalfa (8,24,47), lupine (23), lentils (23), wheat (92)(93)(94)(95)(96), eggplant (18), and potatoes (59).…”