Purification and Properties of Lipoxygenase in Germinating Sunflower Seeds

An outline for isolating sunflower lipoxygenase (SLO) from germinating seeds is described. With linoleic acid as substrate, SLO optimum pH was 6.2, the temperature of maximum activity was 35°C and the activation energy was 3.4 Kcal/mole. Nordihydroguaiaretic acid was the most effective inhibitor of SLO, while α-tocopherol and diethyldithiocarbamic acid were less effective. Km values for linoleic acid, linolenic acid and methyl linoleate were 6.7, 5.0, and 40.0 μM, respectively. The activity of SLO was lost rapidly at temperatures higher than 50°C. The enzyme was stable when stored at ?20°C or freeze-dried, but not at 4°C in dilute solution. Experiments in micellar solution showed that SLO catalytic power was also maintained in hydrocarbon media with a Km for linoleic acid of 9 mM and a maximum velocity of 36.6 U/mg.