Modulation of firefly luciferase bioluminescence at bioelectrochemical interfaces

This paper describes a method by which the activity of an immobilized enzyme can be modulated electrochemically at an electrode. The particular example studied, involving the enzyme firefly luciferase being immobilized in a gelatin film of thickness <1 mu m, provides a useful model system since changes in the catalytic activity can be measured instantaneously through the natural bioluminescent emission. Using this biointerfacial arrangement, we have been able to demonstrate the reversible switching off and on of the enzyme's activity. Through a series of mechanistic studies, we have been able to determine that the bioluminescence response is modulated (on long time scales) as a consequence of the electrochemical depletion of protons at the electrode interface resulting in a local increase in pH.