Reactivity of [RuIII(hedtra)(H2O)] with thio-amino acids and protease inhibition

Reaction of [RuIII(hedtra)(H2O)] (hedtra = N-hydroxyethylethylenediaminetriacetate) with thio-amino acids, L (L = cysteine, N-acetylcysteine, glutathione and penicilamine), was studied kinetically. Kinetic studies were performed at different concentrations of reactants, pH and temperature. Based on the kinetic results, it is suggested that the formation of S-bound substituted product takes place in a rapid ligand dependent rate determining step. Kinetic data and activation parameters are accounted for operation of an associative mechanism and discussed in reference to the data reported earlier for edta4− (ethylenediaminetetraacetate) complex of ruthenium(III). Results of cysteine protease inhibition studies revealed that inhibition activities of Ru–pac complexes are enzyme specific.