DEVELOPMENTAL-CHANGES OF LIPOXYGENASE AND FATTY-ACID HYDROPEROXIDE LYASE ACTIVITIES IN CULTURED-CELLS OF MARCHANTIA-POLYMORPHA

Lipoxygenase activity in Marchantia polymorpha cells rapidly increased during the lag phase of cell growth. In the logarithmically-growing c ells activity tended to decrease, but again increased in the stationar y phase. The two lipoxygenases enhanced in the lag and the stationary phases were purifed. Then could not be differentiated from each other by their enzymatic properties, such as pH-activity profiles, substrate and product specificities. Furthermore, antibody raised against lipox ygenase purified from the cells in the stationary phase reacted with t he enzyme induced in the lag phase with almost the same reactivity. Fr om these observations and Western immunoblot analysis, it was revealed that the developmental change in the activity during cell growth is c aused by de novo synthesis and degradation of essentially the same hpo xygenase. Enzyme activity which degrades fatty acid hydroperoxides, pr oducts of lipoxygenase, was also detected in the cells. n-Hexanal and 12-oxo-(9Z)-dodeceonoic acid were identified as the products formed fr om linoleic acid 13-hydroperoxide by the degradation enzyme; thus, it was revealed to be a fatty acid hydroperoxide lyase. The lyase activit y was also enhanced synchronously with lipoxygenase activity in the la g phase of cell growth, but no induction was observed during the stati onary phase. Addition of linoleic acid to the cells caused little incr ease in the amount of lipid peroxide at the lag phase, while at the st ationary phase, the addition doubled the amount. Furthermore, higher a mounts of C-6-aldehydes were detected in the cells in the lag phase th an those in the stationary phase. These observations suggest that lipo xygenase in the lag phase is involved in C-6-aldehyde formation in coo peration with fatty acid hydroperoxide lyase, while lipoxygenase in th e stationary phase might exert its role by forming lipid peroxides.