This document discusses clinical enzymology and the use of enzymes in clinical diagnosis and treatment. It notes that enzymes act as biocatalysts and deficiencies can cause metabolic issues. Enzymes have tissue and intracellular specificity indicating the organ involved in disease. Enzyme activity can be inhibited reversibly or irreversibly, which can be used clinically. Enzymes can also be produced in laboratories. The document discusses functional and non-functional plasma enzymes, isoenzymes classified by their composition into true isoenzymes, allo-isoenzymes, and hybrid isoenzymes, and the uses of enzymes in clinical fields like diagnosis, prognosis, and therapy.