DROSOPHILA GLUTATHIONE-S-TRANSFERASE D27 - FUNCTIONAL-ANALYSIS OF 2 CONSECUTIVE TYROSINES NEAR THE N-TERMINUS

The Drosophila glutathione S-transferase D27 (GST D27) has been purifi ed and characterized after direct expression of the intronless gstD27 gene in E. coil. The GST D27 has both conjugation activity against the common substrate 1-chloro-2,4-dinitrobenzene and peroxidase activity against cumene hydroperoxide. Its pH optimum is 8.5 in 0.125 M bis-tri s propane buffer at 22 degrees C. It is more thermal labile than the h uman GST121. The GST D27 has two tyrosines at positions 3 and 4. Both of them appear to be important but neither of them is essential for th e enzyme activity. Thus, other residues may also participate in cataly sis. Tile two tyrosines of GST D27 could also be important in binding to GSH or S-hexyl GSH. Results from in vitro biochemical analyses were confirmed by the in vivo activity-based CDNB growth inhibition analys es. Our results clearly indicate that the Drosophila GST D isozymes ar e different from any of the known mammalian GSTs. (C) 1995 Academic Pr ess, Inc.