CHARACTERIZATION OF PIG-LIVER GLUTATHIONE S-TRANSFERASES USING HPLC-ELECTROSPRAY-IONIZATION MASS-SPECTROMETRY

We have characterized 11 porcine liver cytosolic glutathione S-transfe rase (GST) subunits from their precise molecular mass, immunoreactivit y and partial amino acid sequence. Four Alpha-, six Mu- and one unexpe cted Pi-class GST subunits were found with average molecular masses of 24.984-25.228 kDa, 25.039-25.657 kDa and 23.510 kDa respectively. Mol ecular masses were established using electrospray-ionization mass spec trometry, with a precision of +/-3-4 mass units. Glutathione (GSH) and S-hexylglutathione (ShGSH) were tested as affinity ligands in the pur ification procedure. The binding selectivity of GSH was better than th at of ShGSH, although non-GST proteins were retained on both matrices. As already described in other studies, a number of non-GST proteins b ound to the affinity resins. Two of them were tentatively identified a s mevalonate kinase and carbonyl reductase. The characterization of pi g liver cytosolic GST subunits pattern achieved in this work should co nstitute a useful tool for rapid evaluation of these enzymes' expressi on in modulation studies.