This book provides an introduction to enzymology, emphasizing the central role of enzymes as catalysts of life and mediators of disease. It begins with an introduction to the fundamental principles of enzymology, tracing the historical development of the field and explaining the importance of enzymes in maintaining the intricate biochemical processes necessary for life. The text highlights the unique characteristics of enzymes, including their specificity, efficiency, and ability to regulate complex metabolic networks, providing readers with a solid foundation for both normal physiology and pathological states. The text further explores the clinical relevance of enzymes, detailing their involvement in health and disease. Chapters on clinical enzymology and diagnostic applications explain how specific enzyme activities serve as biomarkers for metabolic, cardiovascular, hepatic, and oncological disorders. Therapeutic applications of enzymes are also presented, covering enzyme replacement therapy, enzyme inhibitors, and other interventions that leverage enzymatic activity for medical treatment. In addition, the book addresses industrial and biotechnological applications, demonstrating how enzymes are utilized as biocatalysts in pharmaceuticals, food processing, biofuels, and environmentally sustainable chemical processes. Finally, the book highlights recent advances in enzymology, including enzyme engineering, immobilization techniques, and computational approaches that are expanding the potential of enzymes in research, medicine, and industry. By integrating foundational concepts with contemporary applications, this book provides a holistic perspective on enzymes as pivotal molecules in biology and biotechnology.