UDP-glucose: (6-methoxy)podophyllotoxin 7-O-glucosyltransferase from suspension cultures of Linum nodiflorum

A. Berim, R. Ebel, B. Schneider, M. Petersen

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

Cell cultures of Linum species store 6-methoxypodophyllotoxin (MPTOX), podophyllotoxin (PTOX) and related lignans as O-glucosides. UDP-glucose:(M)PTOX 7-O-glucosyltransferase has been detected and characterised in protein preparations of suspension-cultured cells of Linum nodiflorum L. (Linaceae). The maximal lignan glucoside contents in the cells are preceded by a rapid increase of the specific glucosyltransferase activity on day six of the culture period. MPTOX glucoside is the major lignan with up to 1.18 mg g of the cell dry wt which is more than 30-fold of the PTOX glucoside content. Of the three aryltetralin lignans tested as substrates, PTOX and MPTOX display comparable apparent K values of 4.7 and 5.4 µM, respectively. 5'-Demethoxy-6-methoxypodophyllotoxin is converted with the highest velocity of 25.2 pkat mg while also possessing a higher K of 14.7 µM. Two-substrate test series indicate that all three compounds compete for the active site of a single protein. The structurally similar lignan ß-peltatin acts as competitive inhibitor as well. However, the 6-O-glucosidation is most likely catalysed by a separate enzyme. The (M)PTOX 7-O-glucosyltransferase works best at a pH around 9 and a temperature around 35 °C. A 15-30% increase of the reaction rate is effected by the addition of 0.9 mM Mn.
Original languageEnglish
Pages (from-to)374-381
Number of pages8
JournalPhytochemistry
Volume69
Issue number2
DOIs
Publication statusPublished - Jan 2008

Keywords

  • Linum nodiflorum L.
  • linaceae
  • lignans
  • glucosyltransferase
  • 6-methoxypodophyllotoxin
  • podophyllotoxin
  • ß-Peltatin

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