STEREOSELECTIVE CONJUGATION OF 2-BROMOCARBOXYLIC ACIDS AND THEIR UREA DERIVATIVES BY RAT-LIVER GLUTATHIONE TRANSFERASE 12-12 AND SOME OTHER ISOFORMS

Glutathione (GSH) conjugation of the separate enantiomers of five 2-bromocarboxylic acids and some of their urea derivatives by rat liver GSH transferases (GSTs) was studied. The liver cytosolic fraction conjugated all compound's. except for (R)-2-bromoisovaleric acid, with a variable degree of stereoselectivity. A GST pool, prepared by S-hexyl-GSH affinity chromatography, conjugated the urea derivatives at a somewhat higher rate but had very little activity towards the carboxylic acids, indicating that much activity towards the latter substrates was due to transferases not bound by the affinity column. Therefore, the activity was studied of some pure GSTs that are bound only slightly by the affinity column towards the separate enantiomers of 2-bromovaleric acid (BV), its urea derivative and 2-bromo-3-phenylpropionic acid (BPP). No activity was detected with transferases 5-5 and 8-8. Transferase 1-1 was active towards all compounds with high activity towards the urea derivatives. Transferase 12-12 showed high, stereospecific activity towards the R enantiomers of BV, its urea derivative and BPP.