A method is presented for screening high-density arrays to discover peptides that bind and modulate enzyme activity. A polyvinyl alcohol solution was applied to array surfaces to limit the diffusion of product molecules released from enzymatic reactions, allowing the simultaneous measurement of enzyme activity and binding at each peptide spot. For proof of concept, it was possible to identify peptides that bound to horseradish peroxidase, alkaline phosphatase, and beta-galactosidase and substantially altered enzyme activity by comparing the binding level of peptide to enzyme and bound enzyme activity. This basic technique may be generally applicable to find peptides or other small molecules that modify enzyme activity.