Vacuolar Uptake of the Phytoalexin Medicarpin by the Glutathione Conjugate Pump

Phytochemistry. 1997 Jun;45(4):689-93. doi: 10.1016/s0031-9422(97)00031-9.

Abstract

We have studied the uptake of [3H]-medicarpin and its glutathione conjugate(s) into vacuolar membrane vesicles from etiolated hypocotyls of mung bean (Vigna radiata). Unconjugated medicarpin is taken up at a low rate in the presence or absence of MgATP. However, [3H]-medicarpin-glutathione conjugate(s), prepared by incubation of medicarpin with a total maize glutathione S-transferase preparation, is taken up more than four-fold faster than medicarpin in the presence of MgATP, and this uptake is MgATP-dependent. Uptake of medicarpin-glutathione was not significantly inhibited by the ionophore gramicidin-D, but was strongly inhibited by vanadate and the alternative transport substrate S-(2,4-dinitrophenyl) glutathione. Our results demonstrate, in a model system, the potential utilization of the high affinity, high capacity, uncoupler-insensitive glutathione conjugate pump for the vacuolar transport of an isoflavonoid phytoalexin.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenosine Triphosphate / pharmacology
  • Benzopyrans / metabolism*
  • Fabaceae / metabolism*
  • Glutathione / metabolism*
  • Glutathione Transferase / metabolism
  • Plants, Medicinal*
  • Pterocarpans*
  • Tritium
  • Vacuoles / metabolism*
  • Zea mays / enzymology

Substances

  • Benzopyrans
  • Pterocarpans
  • Tritium
  • medicarpin
  • Adenosine Triphosphate
  • Glutathione Transferase
  • Glutathione