DETOXIFICATION OF XENOBIOTICS BY PLANT-CELLS - CHARACTERIZATION OF VACUOLAR AMPHIPHILIC ORGANIC ANION TRANSPORTERS

The transport activities of two primary ATP-dependent organic-anion tr ansporters in the tonoplast of isolated barley (Hordeum vulgare L. cv. Klaxon) vacuoles have been characterised with N-ethylmaleimide glutat hione (NEM-SG) and taurocholate as substrates. The transporters showed different sensitivities to organic anions and a variety of transport inhibitors and drugs. The vacuolar uptake of NEM-SG was inhibited by c arbonylcyanide 4-trifluoromethoxyphenylhydrazone, 4,4'-diisothiocyanat ostilbene-2,2'-disulfonic acid (DIDS), S-(2,4-dinitrophenyl)glutathion e, alkyl-S-glutathione derivatives and taurocholate but stimulated by probenecid. The uptake of taurocholate was inhibited by vinblastine, D IDS and probenecid. Both transporters were unaffected by verapamil. Th e kinetic properties of the transporters indicate a general preference for amphiphilic anions with some substrate overlap. These characteris tics of the transporters are similar to those displayed by the multidr ug resistance protein of mammalian drug-resistant cells. We suggest th at these vacuolar transporters be described as plant multispecific org anic anion transporters (pMOATs).