Our biological system is enriched with enzyme-catalyzed (or enzymatic) reactions that mediate a great multitude of life processes such as gene transcription and metabolism, and the inappropriately up-regulated activity of these enzymatic reactions is a major cause of human diseases such as cancer and metabolic diseases. Therefore, the inhibitors of enzymatic reactions (generally called enzyme inhibitors) constitute a major class of therapeutic agents on the global drug market. One question would then be how to efficiently design enzyme inhibitors. This handbook is the first of its kind in the field, introducing to its readers in a single book the concepts whose exploitation has been demonstrated to be successful in efficiently furnishing effective active site-directed inhibitors for various enzymatic reactions. The book is organized by different concepts and for each concept there is a delineation of its mode of working and its applications with different types of enzymatic reactions. Active Site-directed Enzyme Inhibitors will help its readers to quickly and efficiently obtain effective active site-directed inhibitors for any of the enzymatic reactions under study without a need to resort to library screening- and biostructure-based techniques. This handbook is ideal as an immediate resource for researchers to consult or for students to supplement their study in medicinal chemistry and related courses.