Jphtm. Ploemen et al., IN-VITRO INHIBITION OF RAT AND HUMAN GLUTATHIONE-S-TRANSFERASE ISOENZYMES BY DISULFIRAM AND DIETHYLDITHIOCARBAMATE, Biochemical pharmacology, 52(2), 1996, pp. 197-204
The drug disulfiram (DSF, Antabuse(R)) has been used in the therapy of
alcohol abuse. It is a potent inhibitor of aldehyde dehydrogenase. It
s reduced form, diethyldithiocarbamate (DDTC), and further metabolites
show similar activities. DSF and DDTC have also been widely used to i
nhibit mixed-function oxidases. In this study, the reversible inhibiti
on and time-dependent inactivation of the major rat and human glutathi
one S-transferase (GST) isoenzymes by DSF and DDTC was investigated. R
eversible inhibition, using 1-chloro-2,4-dinitrobenzene as substrate f
or the GST alpha-, mu-, and pi-class, expressed as I-50 (in mu M), ran
ged from 5-18 (human Al-1), 43-57 (rat 4-4) and 66-83 (rat 1-1), for b
oth DSF and DDTC. The I-50 for rat GST theta, using 1,2-epoxy-3-(p-nit
rophenoxy)-propane as substrate, was 350 mu M for DDTC. The other GSTs
were significantly less sensitive to inhibition. The major part of re
versible inhibition by DSF was shown to be due to DDTC, formed rapidly
upon reduction of DSF by the glutathione (GSH) present in the assay t
o measure GST activity. The oxidized GSH formed upon reduction of DSF
might also have made a minor contribution to reversible inhibition. Th
e rat and human pi-class was, by far, the most: sensitive class for ti
me dependent inactivation by DSF, but no such inactivation was observe
d for any of the GSTs by DDTC. Moderate susceptibility to inactivation
by DSF of all the other GSTs was observed, except for human A2-2, whi
ch does not possess a cysteine residue. Consistent with the assumption
that a thiol residue is involved in this inactivation, a significant
part of the activity could be restored by treatment of the inactivated
GST with GSH or dithiotreitol.