ASTAspartate aminotransferase · SGOT
An enzyme found in liver, heart and muscle, so a raised value is not automatically the liver.
Aspartate aminotransferase is an enzyme that helps cells process amino acids. It sits inside liver cells but also in heart muscle, skeletal muscle and red blood cells, and leaks into the blood when any of those are damaged.
It matters because that spread of sources is the whole point of measuring it beside ALT, which is far more specific to the liver. Hard exercise, a muscle injury or a bruised sample can all raise AST with a perfectly healthy liver, and the ratio between AST and ALT is itself informative.
In practice a raised AST is read alongside ALT, gamma GT and creatine kinase to work out which tissue it came from, and recent heavy training is worth mentioning before a liver is suspected.