title: UDP-glucose:digitoxin 16'-O-glucosyltransferase from suspension-cultured Digitalis lanata cells.
abstract: Suspension cultures from several cell lines of Digitalis lanata, as well as cultures from 6 other plant species were checked for their ability to form purpurea-glycoside A from digitoxin. An in-vitro assay for the UDP-glucose:digitoxin 16'-O-glucosyltransferase (DGT, EC 2.4.1.-) has been established based on an HPLC method. The enzyme is located in the soluble fraction. Its pH optimum is at 7.4. No enzyme activity was found in either purified vacuole preparations or lysed vacuoles. Ascorbate (10 mM) increased the transferase activity about 4-fold. Of the sugar nucleotides tested, only UDP-glucose served as a glucosyl donor. Digitoxin, digoxin, α -acetyldigitoxin, and α-acetyldigoxin are substrates for the glucosyltransferase. The role of the DGT during the biotransformation of cardenolides in Digitalis lanata cell suspension cultures is discussed.
authors.affiliation: Pharmazeutisches Institut (Pharmazeutische Biologie) der Universität Tübingen, Auf der Morgenstelle 8, D-7400, Tübingen, FRG.
authors.forename: W
authors.initials: W
authors.lastname: Kreis
authors.forename: U
authors.initials: U
authors.lastname: May
authors.forename: E
authors.initials: E
authors.lastname: Reinhard