APPEARANCE OF NEW LIPOXYGENASE ISOZYMES DURING SEEDLING GERMINATION OF VICIA-SATIVA

This study describes changes in lipoxygenase and fatty acid lyase activities during seedling germination of Vicia sativa. The two activities showed a concomitant decrease from 0 to 25 h post germination, increased again until 48 h and then showed a simultaneous decrease by day 3. Enzymatically active proteins from 48-h-old seedlings were isolated and the increases of the two activities were shown to be mainly due to the presence of three new lipoxygenase isozymes, designated P-1, P-2 and P-3. They have been partially purified using DEAE trisacryl and Sephadex G-200 chromatographies. The three isozymes exhibit both dioxygenase and fatty acid lyase activities. Lipoxygenase P-1 produced both 13(S)-hydroperoxy-9,11-octadecadienoic acid (13S-HPOD) and 9(S)-hydroperoxy-10,12-octadecadienoic (9S-HPOD) at a ratio of 47:53; lipoxygenase P-2 preferentially produced 9S-HPOD to 13S-HPOD (93:7); whereas lipoxygenase P-3 converted linoleic acid into 13S-HPOD (60%) and 9S-HPOD (40%). In both cases, the reaction product of linoleic acid from fatty acid lyase activity was trans-2, cis-4-decadienal. All three isozymes have pH optima at 5.8 and have no activity at pH 9 for dioxygenase and fatty acid lyase activities.