Prostaglandins containing an
,
-unsaturated ketogroup, such as prostaglandin A
2(PGA
2)and prostaglandin J
2 (PGJ
2), inhibit cellproliferation. These cyclopentenone prostaglandinsmay be conjugated with GSH chemically or enzymatically via glutathioneS-transferases, andthis has been suggested to result in inhibition of theantiproliferative mode of action. In thepresent study, the role of the major human GSTs in the conjugation o
fPGA2 and PGJ
2 withGSH was investigated with purified enzymes,
i.
e.,the Alpha-class enzymes GST A1-1 andGST A2-2, the Mu-class enzyme GST M1a-1a, and the Pi-class enzyme GSTP1-1. The GSHconjugates were separated from the parent compound by HPLC andidentified by fast atombombardment mass spectrometry and
1H-NMR. Two GSHconjugates were found for bothPGA
2 and PGJ
2, the
R- and
S-GSH conjugates of both prostaglandins. Incubationexperimentswith PGA
2 and PGJ
2 (70-600
M) clearlyshowed the role of individual GSTs in the conjugationof PGA
2 and PGJ
2. Compared to the chemicalreaction, enzyme activities towards PGA
2 wereup to 5.4 times as high (GSTA1-1) at the lowest concentration (70
M), while at the highestconcentration (600
M) enzyme activities were up to 3.0 times as high(GST P1-1). For PGJ
2,enzyme activities were up to 4.3 (GSTM1a-1a, 70
M) and up to 3.1(GSTM1a-1a, 600
M)times as high. As expected, similar amounts of the
R-and
S-conjugates of both prostaglandinswere found in the chemical reaction. Striking stereoselectivitiesin conjugating activities wereobserved for GST A1-1 and GST P1-1. GST A1-1 favors the formationof the
R-GSH conjugatesof both prostaglandins. GST P1-1 showed a clear selectivity withregard to the formation ofthe
S-GSH conjugate of PGA
2. However, thisselectivity was not found for the formation ofthe
S-GSH conjugate of PGJ
2. GSTM1a-1ashowed no stereoselectivity with regard to theGSH conjugation of both PGA
2 and PGJ
2.GSTA2-2 only showed some minor formation of the
R-GSH conjugate of PGJ
2. The possibleimplications of the observed stereoselectivity on theeffects of PGA
2 and PGJ
2 arediscussed.