OLEATE DESATURASE ACTIVITY IN SUNFLOWER (HELIANTHUS-ANNUUS) SEEDS ANDITS RELATION TO ASSOCIATED CONSTITUENTS DURING SEED DEVELOPMENT

The locus and specific activity of oleate desaturase (ODS) activity of developing sunflower seeds has been studied using differential centri fugation. The ratio of activity recovered in the crude pellet, oil bod y and microsomal fractions was consistently about 3:1:2 throughout see d development. Microsomes always contained the highest specific activi ty of the enzyme, reaching a maximum at 20-25 days after flowering and declining rapidly thereafter. The change in desaturase specific activ ity (in vitro) with seed development slightly preceded linoleate accum ulation (in vivo) but was synchronous with the changing levels of cyto chrome b. Although the associated metabolic enzymes CDP-choline:1,2-di acylglycerol cholinephosphotransferase (CPT) and acyl-CoA:lysophosphat idylcholine acyltransferase (LPCAT) reached maximum activities at the same time as the desaturase enzyme, these activities decreased less ma rkedly during subsequent seed maturation. An unrelated microsomal enzy me, NADPH-cytochrome c-reductase (NCR), did not reach maximal activiti es until 40 days after flowering.