The interaction between α2-macroglobulin and cationic aspartate aminotransferase

On starch-gel or polyacrylamide-gel electrophoresis of human serum, a supernumerary zone of aspartate aminotransferase activity may be demonstrated, migrating with the slow α2 protein zone. This appearance is due only to cationic aspartate aminotransferase, bound by α2-macroglobulin. The binding is strongly potentiated by dilute borate buffers.