MICELLE-SUPPORTED ELECTROENZYMOLOGY - SUCCINATE DEHYDROGENATION BY ESCHERICHIA-COLI FUMARATE REDUCTASE IN DECYLUBIQUINONE AND OCTYL GLUCOSIDE MICELLES

The concept of micelle-supported electroenzymology is demonstrated usi ng a system consisting of the membrane enzyme Escherichia coli fumarat e reductase (FRD), the amphiphilic coenzyme analogue decylubiquinone ( DU), the micelle-forming surfactant n-octyl glucoside (OG), and a gold electrode. The OG micelles provide a hydrophobic, membrane mimetic me dium for FRD and DU to exchange electrons while the gold electrode ser ves to regenerate DU. When succinate is presented to the FRD/DU/OG mic elle system, electroenzymatic oxidation of succinate to fumarate occur s as evidenced using cyclic voltammetry. DU is shown to be the only el ectroactive species in the system; and as increasing amounts of succin ate are added, the expected increase in the peak anodic (oxidative) cu rrent and decrease in the peak cathodic (reductive) current are observ ed. The peak anodic current approaches a limiting value with succinate concentration in qualitative agreement with simple Michaelis-Menten e nzyme kinetics. When the strong competitive inhibitor oxaloacetate is added, enzymatic oxidation of succinate is inhibited as indicated by n o change in the peak anodic and cathodic currents with increasing succ inate concentration.