Toxic effects of several mercury compounds on SHand non-SH enzymes

The toxic effects of several mercury compounds on the activities of horse liver alcohol dehydrogenase (an SH-enzyme) and bovine pancreatic trypsin (a non-SH enzyme) have been studied.Non-competitive type inhibition of the alcohol dehydrogenase activity was observed, and the K_i values were calculated to be of the order of 10^?7 M, 10^?6 M and 10^?5 M for mercuric chloride, monosubstituted and disubstituted mercury compounds, respectively.On the other hand, competitive type inhibition of the activity of trypsin was found, and the K_i values were of the order of 10^?6 M and 10^?4 -10^?5 M for mercuric chloride and monosubstituted mercury compounds, respectively (the disubstituted compound could not be tested for technical reasons). These results indicate that the enzymatic activities depend on the level of substitution of mercury compounds, and the SH-enzyme was found to be more sensitive to every mercury compound tested than the non-SH enzyme.These findings may reflect the degrees of toxicity of these mercury compounds in mammalian tissues.