Alanine (ALT) and aspartate (AST) aminotransferases are standard-of-care biomarkers for liver injury though their temporal dynamics during injury and resolution remain incompletely characterized. Here, we analyze aminotransferase kinetics to determine whether rate laws can be ascertained during acute liver injury agnostic to etiology. From 6.5 million AST and ALT measurements in 91,086 patients, we identify a single rate-limiting step in transaminase decline enabling the discovery of plasma clearance rates of AST (1.13 days