Some enzymes are known for their ability to create macrocomplexes with plasma proteins. Alpha-amylase, creatine kinase, lactate dehydrogenase, or rarely aspartate aminotrasferase (AST) rank among such enzymes. Some of immunoglobulines or possibly their combination partake in the composition of the complex. The macrocomplex possess a substantially larger molecular weight, its degradation is reduced, it is more accumulated in the blood circulation and the particular enzymatic activity in plasma is elevated. Randomly,we have found a 17-year-old girl with an AST hyperactivity. Occurence of the AST macrocomplex with immunoglobulines was detected by a special laboratory investigation. No other laboratory or clinical abnormalities were found in the patient. Health conditions of the girl were followed up in a long-term study and laboratory picture of the macrocomplex did not change during and after six years. Electrophoresis of the AST isoenzymes denoted a different electrophoretic mobility of the macroenzyme when compared to both cytoplasmatic and mitochondrial enzyme.A different molecular weight of the macrocomplex and the free enzyme was proved using Sephadex gel filtration.A share of the particular immunoglobuline classes was determinated by means of immunochemical diffusion technique.

        Key words: aspartate aminotransferase, macrocomplex of AST, immunocomplexes of enzymes, isoenzymes.