EVIDENCE FOR THE PRESENCE OF GPI-ANCHORED PM-NR IN LEAVES OF BETA-VULGARIS AND FOR PM-NR IN BARLEY LEAVES

In green tissues from sugar beet (Beta vulgaris L.) and barley (Hordet um vulgare L.) a plasma membrane bound nitrate reductase (PM-NR) was f ound, This form of nitrate reductase is a hydrophobic enzyme while the soluble nitrate reductase (NR, EC 1.6.6.1) is hydrophilic. The hydrop hobicity was demonstrated using Triton X-114 temperature induced phase separation, hydrophobic interaction chromatography and stimulation of the activity in the presence of phospholipids. For sugar beet PM-NR i t has been shown that this protein is attached to the plasma membrane via a glycosyl-phosphatidylinositol anchor. This is the first report o f such a membrane linkage in green tissues of higher plants.