Aspartate aminotransferase (AST) is an enzyme present in the liver, heart, muscles, and other tissues. It enters the bloodstream when cells are damaged, making it a valuable marker for evaluating liver injury and other tissue damage. Elevated AST levels are commonly observed in liver conditions such as hepatitis or fatty liver disease but can also indicate muscle injury or heart disease. AST is usually assessed alongside alanine aminotransferase (ALT) to more accurately determine the type and severity of liver damage.