Heterogeneity and developmental changes of lipoxygenase in etiolated lentil seedlings

Abstract

Lipoxygenase activity in developing etiolated lentil seedlings showed a continuous decline in the cotyledons, whereas the lipoxygenase activity in the expanding tissues increased up to 6 days after germination, followed by a decrease. SDS-PAGE and IEF analysis showed the presence of at least two different lipoxygenases in the cotyledons and of four distributed over the vegetative parts. Characterization of these six lipoxygenases after partial purification showed that they differed in p I, molecular mass, substrate preference and product specificity. The products obtained by incubating linoleic acid with these lipoxygenases were analysed by straight phase HPLC and chiral phase HPLC. One of the seed lipoxygenases and two shoot-tip specific lipoxygenases synthesized mainly 13-( S)-hydroperoxy-(9 Z,11 E)-octadecadienoic acid. The other seed lipoxygenase and a root specific lipoxygenase synthesized 9-( R)-hydroperoxy-(10 E,12 Z)-octadecadienoic acid and 13-( S)-hydroperoxy-(9 Z,11 E)-octadecadienoic acid in a molar ratio of 2:1 and produced also oxodienes. A lipoxygenase found in the lower part of the epicotyl and in the hypocotyl synthesized 13-( S)-hydroperoxy-(9 Z,11 E)-octadecadienoic acid and oxodienes.