Conjugation of anti-dihydrodiol epoxides of benzo[a]pyrene, chrysene, benzo[c]phenanthrene and dibenz[a,h]anthracene with glutathione catalyzed by cytosol and by the Mu-class glutathione transferase HTP II from rat liver.
The (+/-)-anti-dihydrodiol epoxides (DE) of benzo[a]pyrene (BP), chrysene (Chr), benzo[c]phenanthrene (BcPh) and dibenz[a,h]anthracene (DBA) were incubated in the presence of glutathione (GSH) with hepatic cytosol from untreated and Aroclor 1254 pretreated rats and with the Mu-class glutathione transferase (GST) HTP II from rat liver. The diastereoisomeric GSH conjugates formed were separated, identified and quantified by HPLC employing synthetic reference compounds. All (+/-)-anti-dihydrodiol epoxides investigated in this study were proven to be substrates of the cytosolic GSTs. The highly mutagenic and carcinogenic (+)-anti-DE with R,S,S,R absolute configuration was preferentially conjugated in the case of BP and Chr. Aroclor 1254 pretreatment increased the turnover 2-3-fold and changed the enantioselectivity. The previously purified GST HTP II exhibited a high degree of enantioselectivity (> or = 95%) towards the R,S,S,R-configurated enantiomer in the case of the bay-region (+/-)-anti-BPDE, (+/-)-anti-ChrDE and (+/-)-anti-DBADE, whereas in the case of fjord-region (+/-)-anti-BcPhDE both enantiomers were good substrates. The contribution of HTP II to the enzymatic activity of the cytosolic GST pool was estimated to be in the range of 11-32%. In agreement with previous results, the observed enantioselectivity of the purified enzyme seems to be of minor significance considering the total GST pool in the liver.
Funk
M
M
Institute of Toxicology, University of Mainz, Germany.
Gath
I
I
Seidel
A
A
Oesch
F
F
Platt
K L
KL
D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide / Q000378:metabolism*; D000818:Animals; D001140:Aroclors / Q000494:pharmacology; D001551:Benz(a)Anthracenes / Q000378:metabolism*; D002273:Carcinogens / Q000494:pharmacology; D002384:Catalysis; D020111:Chlorodiphenyl (54% Chlorine); D002911:Chrysenes / Q000378:metabolism*; D003600:Cytosol / Q000201:enzymology; D005978:Glutathione / Q000378:metabolism*; D005982:Glutathione Transferase / Q000378:metabolism*; D007527:Isoenzymes / Q000378:metabolism*; D008099:Liver / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D010616:Phenanthrenes / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013237:Stereoisomerism
D001140:Aroclors; D001551:Benz(a)Anthracenes; D002273:Carcinogens; D002911:Chrysenes; D007527:Isoenzymes; D010616:Phenanthrenes; D020111:Chlorodiphenyl (54% Chlorine); C090203:1,2-epoxy-3,4-dihydroxy-1,2,3,4-tetrahydrobenzo(c)phenanthrene; D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide; C021977:chrysene,2-diol-3,4-epoxide-1; C079613:dibenz(a,h)anthracene-3,4-diol 1,2-oxide; D005982:Glutathione Transferase; D005978:Glutathione