Book excerpt: Therapeutic enzymes exhibit fascinating features and opportunities, and represent a significant and promising subcategory of modern biopharmaceuticals for the treatment of several severe diseases. Research and drug developments efforts and the advancements in biotechnology over the past twenty years have greatly assisted the introduction of efficient and safe enzyme-based therapies for a range of both rare and common disorders. The introduction and regulatory approval of twenty different recombinant enzymes has enabled effective enzyme-replacement therapy. This volume aims to overview these therapeutic enzymes, focusing in particular on more recently approved enzymes produced by recombinant DNA technology. This volume is composed of four sections. Section 1 provides an overview of the production process and biochemical characterization of therapeutic enzymes, while Section 2 focuses upon the engineering strategies and delivery methods of therapeutic enzymes. Section 3 highlights the clinical applications of approved therapeutic enzymes, including aspects on their structure, indications and mechanisms of action. Together with information on these mechanisms, safety and immunogenicity issues and various adverse events of the recombinant enzymes used for therapy are discussed. Section 4, provides discussion on the prospective and future developments of new therapeutic enzymes. This book is aimed at academics, researchers and students undertaking advanced undergraduate/postgraduate programs in the biopharmaceutical/biotechnology area who wish to gain a comprehensive understanding of enzyme-based therapeutic molecules.