Subcellular localization of udpg: Nuatigenin glucosyltransferase in oat leaves

Cell-free enzyme preparations from oat leaves effectively catalyse the conversion of both phytosterols and nuatigenin (a furostanol sapogenin) to the corresponding 3β-d-glucosides, with UDPG acting as a sugar donor. Subcellular fractionation has shown that UDPG: sterol glucosyltransferase activity is present almost exclusively in the membranous fraction (105 000 g pellet) while a large part (ca 70 %) of UDPG : nuatigenin glucosyltransferase activity occurs in the cytosol (105 000 g supernatant). The results obtained indicate clearly that oat leaves contain at least two UDPG-dependent glucosyltransferases catalysing glucosylation of 3β-hydroxysteroids which are localized in different cell compartments and exhibit different specifirity patterns.