ABSTRACT
Dysregulation of specific enzymes, such as proteases, protein kinases, and protein phosphatases, has been implicated in various pathological conditions, especially malignancies. Therefore, much effort has been directed towards developing potent inhibitors of specific enzymes for cancer chemoprevention. However, many of these compounds are broad-spectrum inhibitors that show undesirable side effects among these closely related enzymes. Thus, there is still a considerable need for more selective inhibitors and for new and high-quality treatments. A better understanding of substrate specificities of these enzymes may significantly improve our overall knowledge about these enzymes, and this will facilitate the design and optimization of potent and selective inhibitors. In recent years, high-throughput screening (HTS), where hundreds of thousands of compounds can be tested for activity during a short period, has been increasingly used to discover novel lead candidate molecules. A key step in establishing an HTS format is to identify a highly selective substrate for use in enzyme assays. A basic understanding of substrate preferences allows further clarification of the physiological roles of these enzymes.
