The Physiological Sources of, Clinical Significance of, and Laboratory-Testing Methods for Determining Enzyme Levels

Enzymes are organic molecules that accelerate biochemical reactions but emerge from the reaction unchanged. Abnormal levels of plasma enzymes are highly suggestive of damaged cells and provide clues to parts of the body that may be involved in disease processes. Enzyme levels are measured in the clinical laboratory to identify the site of damage and to quantify the amount of damage. This paper will discuss the physiological sources, clinical significance, and laboratory-testing methodology for lactate dehydrogenase (LD), aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), and gamma-glutamyltransferase (GGT).