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The History of AST

Aspartate aminotransferase was originally known as serum glutamic-oxaloacetic transaminase, or SGOT, and its clinical story began in 1954, when researchers Felix Wroblewski and John LaDue at New York University discovered that this enzyme surged dramatically in the blood of patients who had just suffered a heart attack. Their landmark finding, published the following year in a major medical journal, gave physicians their first reliable blood test for detecting damage to heart muscle, transforming cardiac diagnosis almost overnight in an era when doctors otherwise had to rely mainly on symptoms and slower-developing changes on an electrocardiogram tracing. Not long after, researchers realized the same enzyme also rose sharply with liver damage and muscle injury, considerably expanding its clinical usefulness well beyond the heart alone and into general internal medicine practice worldwide.

What AST Actually Is

AST is an enzyme found in many tissues throughout the body, including the liver, heart muscle, skeletal muscle, kidneys, and red blood cells, where it plays a role in amino acid metabolism by transferring a chemical group between two molecules involved in the body's central energy-producing pathways. Because it exists in so many different tissues, an elevated AST level alone cannot pinpoint exactly which organ is under stress, which is why doctors typically interpret it alongside ALT, a more liver-specific enzyme, to help narrow down whether an abnormal result points toward the liver, the heart, or muscle tissue elsewhere in the body. The ratio between the two enzymes itself often carries diagnostic meaning that neither individual value provides entirely on its own to a clinician.

How AST Is Measured

Modern laboratories measure AST using a kinetic enzymatic assay nearly identical in principle to the one used for ALT: a coupled chemical reaction consumes a light-absorbing compound called NADH at a rate directly proportional to how much AST is present, and a spectrophotometer tracks that change precisely over just a few seconds of reaction time. This method, standardized internationally by the International Federation of Clinical Chemistry, replaced older and far less precise techniques from the 1950s that made comparing results across different hospitals and laboratories notoriously unreliable, especially when tracking a single patient's trend over multiple visits spanning weeks or months of ongoing medical care.

Scientists Behind the Science

Felix Wroblewski and John LaDue's 1954 discovery is widely regarded as the founding moment of modern enzyme diagnostics, proving for the first time that a simple blood test could detect silent internal organ damage well before other clinical signs became obvious to an examining physician at the bedside. Arthur Karmen, working in the same research environment at NYU, developed the precise spectrophotometric technique that made rapid, standardized transaminase testing practical for routine hospital use, and early results were even reported in "Karmen units" before international standard units were later adopted worldwide. Together, their combined work helped establish enzyme testing as a genuine cornerstone of modern laboratory medicine, a principle now applied to dozens of other diagnostic blood tests used every single day in hospitals everywhere around the globe.