Vacuolar transport of the glutathione conjugate of trans-cinnamic acid.
Red beet (Beta vulgaris L.) tonoplast membrane vesicles and [14C]trans-cinnamic acid-glutatione were used to study the vacuolar transport of phynylpropanoid-glutathione conjugates which are formed in peroxidase-mediated reactions. It was determined that the uptake of [14C]trans-cinnamic acid-glutathione into the tonoplast membrane vesicles was MgATP dependent and was 10-fold faster than the uptake of non-conjugated [14C]trans-cinnamic acid. Uptake of the conjugate in the presence of MgATP was not dependent on a trans-tonoblast H+-electrochemical gradient, because uptake was not affected by the addition of NH4Cl (1 mM; 0% inhibition) and was only slightly affected by gramicidin-D (5 microM; 14% inhibition). Uptake of the conjugate was inhibited 92% by the addition of vanadate (1 mM) and 71% by the addition of the model substrate S-(2,4-dinitrophenyl) glutathione (500 microM). Uptake did not occur when a nonhydrolyzable analog of ATP was used in place of MgATP. The calculated Km and Vmax values for uptake were 142 microM amd 5.95 nmol mg(-1) min(-1), respectively. Based on these results, phenylpropanoid-glutation conjugates formed in peroxidase-mediated reactions appear to be transported into the vacuole by the glutathione S-conjugate pump(s) located in the tonoplast membrane.
Walczak
H A
HA
Department of Biological Sciences, DePaul University, Chicago, IL 60614-3238, USA.
Dean
J V
JV
D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D001692:Biological Transport; D019663:Chenopodiaceae / Q000378:metabolism* / Q000648:ultrastructure; D002934:Cinnamates / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism*; D010544:Peroxidases / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism*
D018528:ATP-Binding Cassette Transporters; D002934:Cinnamates; C029010:cinnamic acid; D000255:Adenosine Triphosphate; D010544:Peroxidases; D005978:Glutathione