The mononuclear zinc complex [(bpta)Zn](ClO4)(2)center dot 0.5H(2)O promotes the hydrolysis of the thioester PhCH(OH)C(O)SCD3 when dissolved in CH3CN:H2O (50:50 buffered at pH 9.0). This reaction results in the formation of a mixture of CD3SH and a zinc thiolate complex, the latter of which can be protonated to generate additional CD3SH. Kinetic studies revealed an overall second-order reaction with an activation energy that is similar to that found for aqueous OH-promoted thioester hydrolysis. These studies represent the first investigation of chemistry relevant to that occurring in the monozinc-containing form of human glyoxalase II.