Jg. Correa et Aom. Stoppani, GLUTATHIONE-REDUCTASE INACTIVATION BY CU( II)H2O2 - INFLUENCE OF THIOLS AND CATECHOLAMINES, Anales de la Asociacion Quimica Argentina, 85(5-6), 1997, pp. 217-230
Yeast glutathione reductase (GR) was inactivated by the Cu-Fenton syst
em (FS; Cu(II)/H2O2). Several monothiols, namely cysteine, N-acetylcys
teine, mercaptopropionylglycine) and penicillamine increased GR inacti
vation by the CU(II)H2O2, the inactivation reaching maximum values at
about 0.20 mM thiol. Glutathione (GSH), dithiothreitol, dihydrolipoic
acid and Captopril produced similar effects at concentrations up to ab
out 0.2 mM, but higher concentrations were less effective, specially d
uring short-time incubations. Oxidized GSH (GSSG) and the disulfide tr
ypanothione protected GR against CU(II)H2O2. Generally speaking, the e
ffect of thiols on GR inactivation correlated with the latter compound
s capability for generating hydroxyl radicals, in the presence of CU(I
I)H2O2. Cu(ll)-complexing agents(EDTA and DETAPAC) at adequate concent
rations prevented GR inactivation by CU(II)H2O2. The Cu(II)/RSH system
s (H2O2 omitted) also inactivated GR but to a lesser degree than the c
orresponding CU(II)/H2O2/RSH systems. Superoxide dismutase and catalas
e prevented GR inactivation by the CU(II)/RSH systems thus proving the
role of superoxide radical and H2O2 respectively. Catecholamines (epi
nephrine-nor-epinephrine, Dopamine, 60H-Dopamine, L-DOPA, DOPAC), pyro
gallol and the dicatechol nor-dihydroguaiaretic acid) enhanced, like t
hiols, GR inactivation by CU(II)H2O2 lesser effects were observed with
the Cu(ll)/catecolamines systems (H2O2 omitted). It is concluded that
GR inactivation by the Cu(II)/H2O2/RSH systems depends on a chain of
reaction producing HO-radicals. That chain involves copper ions, super
oxide anions and H2O2. A similar reaction mechanism would operate with
the Cu(ll)/H2O2/catecholamine and related systems.