Macromolecular aspartate aminotransferase.

Macroenzymes are serum enzymes that have a greater molecular mass than the corresponding enzyme normally found in serum (Klonoff. West J Med 1980; 133: 392-407). Serum AST (aspartate aminotransferase) has rarely been reported to complex with immunoglobulins, resulting in an elevation in serum AST activity. Physicians should be aware of this condition so that patients are not subjected to invasive and costly procedures unnecessarily (Litin et al. Mayo Clin Proc 1987; 62: 681-687). We report on such a patient with a raised AST due to macroenzyme formation.