The binding of enzymes into artificial membranes makes possible a study of the interaction between membrane structure and enzyme kinetics within a simple context. Artificial protein membranes bearing a bienzyme system (xanthine oxidase, uricase) are produced by using a co-crosslinking method. The inhibition of uricase was shown to be dependent not only on the concentration of inhibitor in the bulk solution, but also on the kinetic properties of the membrane-bound enzymes. In the presence of xanthine oxidase inside the structure the uricase inhibition by xanthine is less important than in solution. Under defined conditions the activity was found to be higher in the presence of inhibitor than in its absence. Due to diffusion limitations this specific bienzyme system is more efficient when immobilized inside a membrane than when in solution.