Influence of modifications of physicochemical and biological properties of haptoglobin. VII. Immunochemical reactivity of haptoglobin with modified tyrosine residues.

Tyrosine residues in human haptoglobin (Hp) type 2-1 were modified by treatment with various amounts of N-acetylimidazole, iodine or tetranitromethane. Rabbit antisera directed against native Hp, Ac-Hp, 1-Hp and NO2-Hp in cross-reactions by immunoprecipitation showed serologic identify of native Hp and most of the modified derivatives, with the exception of derivatives modified by means of a high excess of N-acetylimidazole, which showed partial identity with remaining preparations, irrespective of the antiserum used. The results indicate that tyrosine residues play no essential role in the immunochemical reactivity of haptoglobin.