Reactions of Organoselenenyl Iodides with Thiouracil Drugs: An Enzyme Mimetic Study on the Inhibition of Iodothyronine Deiodinase.

The proposed mechanism of iodothyronine deiodinase inhibition by the thiourea-derived drugs 6-n-propylthiouracil (PTU) and 6-methylthiouracil is supported by experimental evidence. Model reactions with sterically or coordinatively stabilized organoselenyl iodides as enzyme-mimetic substrates (E-SeI; see scheme) support the proposal that PTU reacts not with the enzyme but with the enzyme-SeI intermediate containing a covalent Se-I bond, and suggest that the Se-I bond is kinetically activated by basic amino acid groups such as histidine.