US EPA

5369798 

Journal Article 

Glutathione Transferase Activity of Vacuoles, Plastides, and Tissue Extracts of Red Beetroot 

Pradedova, EV; Nimaeva, OD; Truchan, IS; Salyaev, RK 

2016 

Yes 

Biologicheskie Membrany
ISSN: 0233-4755 

33 

2 

140-149 

Russian 

10.7868/S0233475516020092 

WOS:000375627600008 

Glutathione transferase activity (GST) was revealed in the red beetroot vacuolar fractions (Beta vulgaris L.). This activity was compared with that of plastids and extracts of red beetroot tissues. The level of GST activity determined by spectrophotometric method proved fairly high both in water extracts and in the membrane fractions of isolated organelles. The pH dependence of GST slightly differed in the objects studied. The vacuolar GST was active at pH ranging from 6.0 to 8.0, with the pH optimum between 7.0- 7.5, while the pH optimum of GST in plastids and tissue extract was pH 7.5. The enzymes of studied objects differed in specificity to substrates fluorodifen and eth- Acrynic acid. The activity of vacuolar and tissue extract GST for fluorodifen was significantly higher than that of the enzymes from plastids. The ethacrynic acid, often used as a competitive inhibitor of GST, almost completely inhibited the GST activity assessed with 1 -chloro-2,4-dinitrobenzene as a substrate. In addition to being an inhibitor of GST, ethacrynic acid also interacts with GST as a substrate. However, ethacrynic acid was a substrate only for GST of vacuoles and tissue extract, but not for GST of plastids. Significant differences were found in substrate specifcity and iso-enzyme composition of GST. In all objects under study several zones of the enzyme activity that could correspond to different iso-enzymes were identified by the clcctrophorctic method. The results suggest that vacuoles with relatively high GST activity make a significant contribution to the processes of intracellular detoxi- cation. The very presence of the enzymes of the GST family indicates that the main function of vacuole is not just deposition and degradation of glutathione conjugates that are re-directed to this compartment for isolation and utilization, as was previously believed. Thanks to a proper GST, conjugates of compounds of the exogenous origin, such as herbicides, may be formed inside vacuole. Another possible function of GST localized in vacuoles may be related to the antioxidant protection, which is indirectly confirmed by the enzyme association with membranes. 

Beta vulgaris; vacuoles; plastides; glutathione-S transferases; xenobiotics; detoxication