Prostaglandins
containing an
chars/alpha.gif" BORDER=0>,
chars/beta2.gif" BORDER=0 ALIGN="middle">-unsaturated ketogroup, su
ch as prostaglandin A
2(PGA
2)and prostaglandin J
2 (PGJ
2), inhibit
cellproliferation. These
cy
clopentenone prostaglandinsmay be
conjugated with GSH
chemi
cally or enzymati
cally via glutathioneS-transferases, andthis has been suggested to result in inhibition of theantiproliferative mode of a
ction. In thepresent study, the role of the major human GSTs in the
conjugation ofPGA
2 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 GSH
conjugates were separated from the parent
compound by HPLC andidentified by fast atombombardment mass spe
ctrometry and
1H-NMR. Two GSH
conjugates were found for bothPGA
2 and PGJ
2, the
R- and
S-GSH
conjugates of both prostaglandins. In
cubationexperimentswith 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
chemi
calrea
ction, enzyme a
ctivities towards PGA
2 wereup to 5.4 times as high (GSTA1-1) at the lowest
con
centration (70
M), while at the highest
con
centration (600
M) enzyme a
ctivities were up to 3.0 times as high(GST P1-1). For PGJ
2,enzyme a
ctivities were up to 4.3 (GSTM1a-1a, 70
M) and up to 3.1(GSTM1a-1a, 600
M)times as high. As expe
cted, similar amounts of the
R-and
S-
conjugates of both prostaglandinswere found in the
chemi
cal rea
ction. Striking stereosele
ctivitiesin
conjugating a
ctivities 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 sele
ctivity withregard to the formation ofthe
S-GSH
conjugate of PGA
2. However, thissele
ctivity was not found for the formation ofthe
S-GSH
conjugate of PGJ
2. GSTM1a-1ashowed no stereosele
ctivity 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 possibleimpli
cations of the observed stereosele
ctivity on theeffe
cts of PGA
2 and PGJ
2 aredis
cussed.