Identification of theta-class glutathione S-transferase in liver cytosol of the marmoset monkey

The presence of theta-class glutathione S-transferase (GST) in marmoset mon key liver cytosol was investigated. An anti-peptide antibody targeted again st the C-terminus of rGSTT1 reacted with a single band in marmoset liver cy tosol that corresponded to a molecular weight of 28 kDa. The intensity of t he immunoreactive band was not affected by treatment of marmoset monkeys wi th 2,3,7,8-tetrachlorodibenzo-p-dioxin, phenobarbitone, rifampicin or clofi bric acid. Similarly, activity towards methyl chloride (MC) was unaffected by these treatments. However, GST activity towards 1,2-epoxy-3-(p-nitrophen oxy)-propane (EPNP) was increased in marmosets treated with phenobarbitone (2.6-fold) and rifampicin (2.6-fold), activity towards dichloromethane (DCM ) was increased by 50% after treatment of marmosets with clofibric acid, an d activity towards 1-chloro-2,4-dinitrobenzene (CDNB) was raised slightly ( 30-42% increases) after treatment with phenobarbitone, rifampicin or clofib ric acid. Compared with humans, marmoset liver cytosol GST activity towards DCM was 18-fold higher, activity towards MC was 7 times higher and activit y towards CDNB was 4 times higher. Further, EPNP activity was clearly detec table in marmoset liver cytosol samples, but was undetectable in human samp les. Immunoreactive marmoset GST was partially purified by affinity chromat ography using hexylglutathione-Sepharose and Orange A resin. The interactio n of immunoreactive marmoset CST was similar to that found previously for r at and human GSTT1, suggesting that this protein is also a theta class GST. However, unlike rat GSTT1, the marmoset enzyme was not the major catalyst of EPNP conjugation. Instead, immunoreactivity was closely associated with activity towards MC. In conclusion, these results provide evidence for the presence of theta-class GST in the marmoset monkey orthologous to rGSTT1 an d hGSTT1.