The first non-turnover voltammetric response from a molybdenum enzyme: direct electrochemistry of dimethylsulfoxide reductase from Rhodobacter capsulatus

The first direct voltammetric response from a molybdenum enzyme under non-turnover conditions is reported. Cyclic voltammetry of dimethylsulfoxide reductase from Rhodobacter capsulatus reveals a reversible Mo(VI/V) response at +161 mV followed by a reversible Mo(V/IV) response at -102 mV versus NHE at pH 8. The higher potential couple exhibits a pH dependence consistent with protonation upon reduction to the Mo(V) state and we have determined the p K(a) for this semi-reduced species to be 9.0. The lower potential couple is pH independent within the range 5