Tag.-Ber., Akad. Landwirtsch.-Wiss. DDR, Berlin (1990) 291, 419 - 423 Hungarian Acadcmy of Sciences, Budapest Plant Protection Institute T. KOMIVES and G. OROS Effects of phenylamide fungicides on the glutathione conjugation system of Phytophthora spp. fungi It is now well established that a number of protective systems exist in living cells to trap and inactivate toxic xenobiotics or to counteract their harmful effects (COHEN et al., 1986; ELLNER, 1987; JAKOBY and HABIG, 1980; KOMIVES and DUTKA, 1989a). The glutathione (y-L-glutamyl-L-cysteinyl-glycine, GSH) conjugation system represents an important pathway to eliminate endogenous or exogenous electrophilic compounds, and its effectiveness may determine pesticide sensitivity or tolerance (COHEN et al., 1986; ELLNER, 1987; JAKOBY and HABIG, 1980; KOMIVES and DUTKA, 1989b). Phenylamides (Table 1) are systemic fungicides active against Pcronosporalcs (DAVIDSE, Table 1 Structure of phenylamide fungicides investigated in this study R 1 R 2 Metalaxyl 1-methoxycarbonyl-cthyl mcthoxy CGA-29212 1-methoxycarbonyl-cthyl chloro Ofurace tctrahydrofuran-2-on-3-yl chloro RE-26745 tetrahydrofuran-2-on-3-yl methoxy Benalaxyl 1-methoxycarbonyl-cthyl benzyl 1987). Structurally related chloroacetanilide herbicides in plants are detoxified by GSH conjugation (Eq. 1) GST GSH + Cl-CH,-CO-NR'R" > GS-CH^-CO-NR'R" (Eq. 1) -HC1 catalyzed by the enzyme glutathione S-transferase (EC 2.5.1.18) (KOMIVES et al., 1985). Since Phytophthora spp. fungi show differential sensitivity (occasionally resistance) to phenylamide fungicides (FISHER and HAYES, 1984; OROS, 1987; DAVIDSE, 1987), and arc typical representatives of the tribe Oomycota evolutionally related to plants (OROS, et al., 1988) this investigation was undertaken to determine if their GSH conjugation