A thiol oxidation interpretation of the Cu2+ effects on rat liver mitochondria

Kinetics of Cu2+ inhibition of Na+K+-ATPase

“…The integral N a+ /K + -ATPase has two a-subunits [6], each containing at least 34 essential sulfhydryl groups in its catalytic center [7]. C u2+ is a well-known potent reagent for thiol groups; its interaction with membrane and enzymatic SH-groups may therefore result in toxic effects [15,16], The ability of the SH-group reducing agent, dithiothreitol (DTT), to protect against C u2+ toxicity would confirm that such groups in the enzyme are a tar get for C u2+, in line with other studies [19,20,30], However, DTT also strongly chelates Cu2+, and evidence was given -comparing DTT with the chelator TPEN which lacks reducing propertiesthat such an effect could also explain the protec tive action of DTT on N a + /K*-ATPase [13], Clearly, both effects of DTT will simultaneously occur in experiments as presented here, and we cannot discriminate one effect from the other.…”

“…Although the toxic action o f Cu2+ is mainly attributed to covalent binding o f C u2+ to functional sulfhydryl (-SH) groups of membrane proteins and enzymes [14][15][16][17], including N a + /K +-ATPase [18][19][20], the kinetics of C u 2+ interaction with N a + /K +-ATPase are flawed by the fact that, in these studies, the total concentration of copper rather than the free C u 2+ concentrations was con sidered. It is generally believed that the ionic form o f copper, C u 2+, represents the toxic form of this metal [16]. The higher affinity of ATP for C u2+ over M g2+ [21] means that little Mg-ATP remains in an assay medium when C u 2+ is added (see Discussion), For a proper in-vitro evaluation of the enzymatic activity, Mg-ATP is required as sub strate and cannot be replaced by Cu-ATP [22].…”

Copper toxicity in cultured human skeletal muscle cells: the involvement of Na+/K+-ATPase and the Na+/Ca2+-exchanger

“…The biochemical mechanism underlying C u2+ toxicity has mainly been related to the oxidation of sulphhydryl groups in membrane proteins [14,23]. Na+ /K+ -ATPase contains many functional sulphhydryl groups and is vul nerable to Cu2+ and other heavy metal ions [20, 22, 29.…”

In vitro modulation of heavy metal-induced rat liver mitochondria dysfunction: A comparison of copper and mercury with cadmium

“…In addition, these findings, together with the data obtained from the swelling experiments (Figs. 1-3 and 5), point to the external site of action of the metals (i.e., from the outer (cytosol) side of the inner membrane) that seems to prevail, as in the case of Cu 2+ (see [36]), in the Hg 2+ toxicity. Seemingly, the same is true for the Cd 2+ effects on the mitochondrial swelling and respiration in K + -acetate-containing medium and in KCl medium in the presence of RR or Ru-360 (Figs.…”