title: Complexes of immunoglobulins A and G with aspartate aminotransferase isoenzymes in serum.
abstract: We report the presence of complexes between aspartate aminotransferase (AST, EC 2.6.1.1) and immunoglobulin (Ig) in the serum of a patient suffering from lung cancer with metastasis to the liver. After fractionation of the serum by gel filtration, AST-Ig complexes (AST-IgA, AST-IgG) were demonstrated by counterimmunoelectrophoresis. Dissociating the complexes and recombining them with purified isoenzyme fractions, s-AST (cytoplasmic) and m-AST (mitochondrial), revealed that only s-AST binds to IgG, whereas IgA binds to both s-AST and m-AST. Although the association of AST with IgG has been reported, to our knowledge this is the first finding of both AST-IgA and AST-IgG complexes in a patient's serum. Serum AST-IgG complexes have been demonstrated in both healthy and diseased individuals; in the latter category, as reported here and by others, the liver is implicated.
mesh_terms: D000368:Aged; D001219:Aspartate Aminotransferases / Q000378:metabolism*; D002850:Chromatography, Gel; D003378:Counterimmunoelectrophoresis; D003593:Cytoplasm / Q000201:enzymology; D006801:Humans; D007070:Immunoglobulin A / Q000378:metabolism*; D007074:Immunoglobulin G / Q000378:metabolism*; D007527:Isoenzymes / Q000378:metabolism*; D008113:Liver Neoplasms / Q000097:blood / Q000556:secondary; D008175:Lung Neoplasms / Q000097:blood; D008297:Male; D008928:Mitochondria / Q000201:enzymology; D011233:Precipitin Tests; D011485:Protein Binding
chemical_list: D007070:Immunoglobulin A; D007074:Immunoglobulin G; D007527:Isoenzymes; D001219:Aspartate Aminotransferases