Reactions of medicinally relevant gold compounds with the C-terminal motif of thioredoxin reductase elucidated by MS analysis.

The tetrapeptide Ac-Gly-[Cys-Sec]-Gly-NH(2), reproducing the C-terminal motif of the selenoenzyme thioredoxin reductase, was designed and synthesized, and its reactions with a few medicinally relevant gold(i,iii) compounds investigated by ESI-MS. Remarkably, the main reaction products could be unambiguously identified providing valuable insight into the likely mechanisms of enzyme inhibition by gold compounds.