摘要
Turning the light on and off can control the activity of xanthine oxidase (XOD) when allopurinol (1) is the substrate. Alloxanthin (2) is formed in the reaction but also acts as an inhibitor of the enzyme. Irradiation can free the active site and let the enzyme get on with its job. The alloxanthin - XOD system might have important future applications as a photoswitch/integrator in molecular-scale optobioelectronic devices.