Characterization and behaviour of 15-lipoxygenase during peanut cotyledonary senescence

Lipoxygenase (EC 1.13.11.12) (LOX), a ubiquitous plant enzyme which catalyzes the hydroperoxidation of unsaturated fatty acids (PUFA), plays an important role during the course of leaf and cotyledonary senescence. In the present study, senescence related changes in chlorophyll and protein content and lipoxygenase activity have been examined in peanut cotyledons. The chlorophyll content of the cotyledons increased from the 2nd to 8th day followed by a steady decline. In contrast, protein content of peanut cotyledons decreased continuously during senescence. Lipoxygenase activity, on the other hand, increased in early stages of germination followed by a decrease in the later course of senescing peanut cotyledons. Analysis of the product profile, the lipoxygenase with arachidonic acid as the substrate on HPLC, has shown a single peak comigrating with standard 15-Hydroperoxyeicosatetraenoic acid. The results on peanut cotyledonary 15-lipoxygenase activity in relation to abscisic acid and kinetin are discussed.