Novel synthetic enzyme substrates, enhanced to have improved enzymatic specificity, are disclosed. These synthetic enzyme substrates consist of a substrate peptide that has had its specificity further improved by additional synthetic moieties, selected by combinatorial chemistry techniques, that act to sterically block non-target enzymes. These "steric restrictor" moieties may be labeled to produce a detectable signal upon enzymatic reaction. These novel substrates are particularly useful for improved enzyme substrate microarrays. Specific applications for improved protease substrate microarrays are discussed. A variety of applications for these improved protease substrate microarrays are also disclosed, including proteomics research, protease discovery, protease binding site characterization, diagnosis of the protease composition of biological samples, monitoring the angiogenic status of a tumor, monitoring the status of arthritis and other inflammatory diseases, and the discovery and optimization of novel drugs that modify or inhibit protease activity.