Mercury(II) binds to both of chymotrypsin's histidines, causing inhibition followed by irreversible denaturation/aggregation.

ABSTRACT: The toxicity of mercury is often attributed to its tight binding to cysteine thiolate anions in vital enzymes. To test our hypothesis that Hg(II) binding to histidine could be a significant factor in mercury's toxic effects, we studied the enzyme chymotrypsin, which lacks free cysteine thiols; we found that chymotrypsin is not only inhibited, but also denatured by Hg(II). We followed the aggregation of denatured enzyme by the increase in visible absorbance due to light scattering. Hg(II)-induced chymotrypsin precipitation increased dramatically above pH 6.5, and free imidazole inhibited this precipitation, implicating histidine-Hg(II) binding in the process of chymotrypsin denaturation/aggregation. Diethylpyrocarbonate (DEPC) blocked chymotrypsin's two histidines (his₄₀ and his<

SUBMITTER: Stratton A 

PROVIDER: S-EPMC5275735 | biostudies-literature | 2017 Feb

REPOSITORIES: biostudies-literature