MASS-SPECTROMETRIC ANALYSIS OF RAT OVARY AND TESTIS CYTOSOLIC GLUTATHIONE S-TRANSFERASES (GSTS) - IDENTIFICATION OF A NOVEL CLASS-ALPHA GST, RGSTA6-ASTERISK, IN RAT TESTIS

Cytosolic glutathione S-transferases (GSTs) from rat ovaries and testi s were purified by a combination of GSH and S-hexylglutathione affinit y chromatography. The isolated GSTs were subjected to reverse-phase HP LC, electrospray MS and N-terminal peptide sequencing analysis. The ma jor GST isoenzymes expressed in ovaries are subunits A3, A4, M1, M2 an d P1. Other isoenzymes detected are subunits Al, M3 and M6. In rat te stis, the major GST isoenzymes expressed are subunits A3, M1, M2, M3, M5 and M6*. Subunits Al, A4 and P1 are expressed in lesser amounts. W e could not detect post-translational modifications of any GSTs with k nown cDNA sequence. The molecular masses of subunits M5 and M6*, two class-Mu GSTs that have not been cloned, were determined to be 25495 a nd 26538 Da respectively. An N-terminally modified protein from rat te stis with molecular mass 25737 Da was isolated from the S-hexylglutath ione column. Results from internal peptide sequencing analysis indicat e that this is a novel class-Alpha GST that has not been previously re ported. We designate this protein rGSTA6.